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SJVDP Reports Library ^^-^-^ ^ 

Rm W-2212 ID No. -^J"^ a/^O/^ 

^^t^^^ RISK ASSESSMENT '' 




KESTERSON 
PROGRAM 



U.S. Bureau of Reclamation 
Mid-Pacific Region 



NOVEMBER 1986 



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RISK ASSESSMENT 
KESTERSON PROGRAM 



Submitted to 
U.S. Bureau of Reclamation, Mid-Pacific Region 



Prepared By 

CH2M HILL 

3840 Rosin Court, Suite 110 

Sacramento, California 95834 

Jones & Stokes Associates 

1725 23rd Street 

Sacramento, California 95816 



November 1986 
M19551.S0 



SAT72/41 



CONTENTS 



Page 



Summary S-1 

Approach 1-1 

Introduction 1-1 

Contamination Evaluation 1-1 

Exposure Assessment 1-1 

Toxicity Assessment 1-2 

Risk Characterization 1-3 

Contamination Evaluation 2-1 
Introduction 2-1 
Past Water Contaminant Concentrations 2-1 
Present Soil and Water Supply Concen- 
trations 2-9 
Biota 2-9 
Identification of Constituents for 

Risk Characterization 2-18 

Exposure Assessment 3-1 

Introduction 3-1 

Cleanup Alternatives 3-1 

Selenium Biogeochemistry 3-2 

Exposure Pathways 3-3 

Exposed Populations 3-4 

Estimates of Trophic Relationships 3-10 

Adaptation for Risk Assessment 3-10 

Toxicology of Selenium 4-1 

Introduction 4-1 

Environmental Sources 4-1 

Birds 4-1 

Mammals 4-5 

Fish 4-6 

Risk Characterization 5-1 

Introduction 5-1 

Kesterson Monte Carlo Model 5-1 

Discussion 5-2 

References 6-1 



Appendix A. Kesterson Reservoir Wildlife 
Species List 



SAT72/85 



TABLES 



Page 



S-1 Percent of Diet Selenium Predictions that are 
Below Estimated Harmful Levels for Each Key 
Species and for Each Cleanup Alternative S-7 

2-1 Water Quality Guidelines and Criteria for 

SWRCB Drain Water Constituents of Concern 2-2 
2-2 San Luis Drain Constituents of Concern at 

Check 2 2-3 

2-3 Kesterson Reservoir Constituents of Concern at 

Surface Water Sites 2-4 

2-4 Kesterson Reservoir Groundwater Summary for 

Constituents of Concern 2-7 

2-5 Summary of Soil Concentrations of Constituents 

of Concern 2-10 

2-6 Quality of Groundwater to be Applied to 

Kesterson Reservoir under FRP 2-11 

2-7 Selenium Concentrations in Composite Samples 

of Invertebrates, May 1983 2-13 

2-8 Summary of Frequencies of Mortality and 

Deformities in Embryos and Chicks of Aquatic 

Birds Nesting at Kesterson Reservoir, 1983-85 2-15 
2-9 Selenium Concentrations in Livers and Whole 

Bodies of Abundant Small Mammal Species from 

Kesterson Reservoir and Volta Wildlife Area 

(Preliminary Data) 2-17 

2-10 Summary of Contaminant Levels in Kesterson 

Reservoir Media 2-19 

3-1 Kesterson Bird Populations and Mortalities 3-8 
3-2 Summary of Data Used to Derive Transfer Factors 3-21 
3-3 Transfer and Diet Factors for Simplified 
Selenium Transfer Diagram for Mallard, 
American Coot, Tricolored Blackbird, and 
Black-Necked Stilt 3-22 

3-4 Transfer and Diet Factors for Simplified 

Selenium Transfer Diagram for Eared Grebe 
and Mosquitofish 3-23 

3-5 Transfer and Diet Factors for Simplified 

Selenium Transfer Diagram for San Joaquin 

Valley Kit Fox 3-24 

4-1 Summary of Dose-Response Reported for Avian 

Species 4-2 

5-1 Percent of Diet Selenium Predictions that are 
below Harmful Levels for Each Key Species 
and for Each Cleanup Alternative 5- 



SAT72/85 



FIGURES 



Pa£e 



S-1 Probability Distribution of Predictions of 

Selenium Concentration in Receptor Species 

Diet for the Flexible Response Plan 5-3 

S-2 Probability Distribution of Predictions of 

Selenium Concentration in Receptor Species 

Diet for the Flexible Response Plan — Onsite-1 5-4 

S-3 Probability Distribution of Predictions of 

Selenium Concentration in Receptor Species 

Diet for the Flexible Response Plan — Onsite-2 5-5 

3-1 Kesterson Reservoir Selenium Transfer Diagram — 

Adult Female Mallard 3-11 

3-2 Kesterson Reservoir Selenium Transfer Diagram — 

Adult Coot 3-12 

3-3 Kesterson Reservoir Selenium Transfer Diagram — 

Tricolored Blackbird (through Fledgling) 3-13 
3-4 Kesterson Reservoir Selenium Transfer Diagram — 

Black-Necked Stilt 3-14 

3-5 Kesterson Reservoir Selenium Transfer Diagram — 

Mosquitofish and Eared Grebe 3-15 

3-6 Kesterson Reservoir Selenium Transfer Diagram — 

Kit Fox 3-16 

3-7 Simplified Selenium Transfer Diagram with Key 

to Transfer and Diet Factors 3-17 

3-8 Simplified Selenium Transfer Diagram with Key 

to Transfer and Diet Factors — Mosquitofish/ 

Eared Grebe 3-18 

3-9 Simplified Selenium Transfer Diagram with Key 

to Transfer and Diet Factors — Kit Fox 3-19 

5-1 Probability Distribution of Predictions of 

Selenium Concentration in Receptor Species 

Diet for the Flexible Response Plan 5-3 

5-2 Probability Distribution of Predictions of 

Selenium Concentration in Receptor Species 

Diet for the Flexible Response Plan — Onsite-1 5-4 

5-3 Probability Distribution of Predictions of 

Selenium Concentration in Receptor Species 

Diet for the Flexible Response Plan — Onsite-2 5-5 

5-4 Probability Distribution of Predictions of 

Selenium Concentration in Receptor Species 

Diet for the Flexible Response Plan — American 

Coot 5-6 

5-5 Probability Distribution of Predictions of 

Selenium Concentration in Receptor Species 

Diet for the Flexible Response Plan — Mallard 507 

5-6 Probability Distribution of Predictions of 

Selenium Concentration in Receptor Species 

Diet for the Flexible Response Plan — 

Black-Necked Stilt 5-8 



SAT72/85 



FIGURES (Cont'd) 



Page 



5-7 Probability Distribution of Predictions of 

Selenium Concentration in Receptor Species 

Diet for the Flexible Response Plan — 

Tricolored Blackbird 5-9 

5-8 Probability Distribution of Predictions of 

Selenium Concentration in Receptor Species 

Diet for the Flexible Response Plan — 

Mosquitofish 5-10 

5-9 Probability Distribution of Predictions of 

Selenium Concentration in Receptor Species 
Diet for the Flexible Response Plan — Eared 
Grebe 5-11 

5-10 Probability Distribution of Predictions of 

Selenium Concentration in Receptor Species 

Diet for the Flexible Response Plan — 

San Joaquin Valley Kit Fox 5-12 

5-11 Probability of Selenium Concentration in 

Receptor Diet Being Less than 3 mg/kg vs. 

Residual Soil Selenium Concentration 5-16 

5-12 Cost vs. Diet Selenixim Concentration for 

Alternative Cleanup Plans 5-18 

5-13 Costs of Alternative Cleanup Plans vs. 

Soil and Diet Selenium 5-19 



SAT72/85 



SUMMARY 



This risk assessment of Kesterson Reservoir (KR) cleanup 
alternatives consists of four elements: 

o Contamination evaluation and determination of con- 
taminants of concern 

o Analysis of exposure pathways, identification of 

key species, and estimates of contaminant transfer 
between pathway components 

o Review of toxicological properties of contaminants 
of concern for key species 

o Risk characterization, including the range of mag- 
nitude of expected exposure and the likelihood of 
such exposure occurring for each cleanup alterna- 
tive 

Review of information related to past and present contamina- 
tion at KR indicates that selenium is a major contaminant of 
concern because, in the past, it has exceeded water quality 
guidelines and criteria, has accumulated in KR soils, has 
migrated into the groundwater in some locations, and has 
been linked experimentally and observationally to wildlife 
effects . 

Other identified constituents of possible concern which have 

exceeded water quality guidelines and criteria include boron, 

chromium, molybdenum, mercury, salts, and zinc. Chromium, 

mercury, molybdenum, and zinc are not of concern because 

these constituents neither appear in KR soils above back- v | ^ 

ground concentrations, nor exceed guidelines and criteria ^ C) 

for KR groundwater supplies. TDS is not of concern because " 

no evidence exists that TDS concentrations in groundwater \V 

supplies will cause adverse wildlife effects in KR. Boron 

is not of concern because no existing evidence has linked 

boron to observed KR wildlife effects; such evidence does 

exist for selenium. 

Three cleanup alternatives were analyzed in detail: the 
Flexible Response Plan (FRP) , the Onsite Disposal Plan-1 
(excavating about 450,000 cubic yards), and the Onsite Dis- 
posal Plan-2 (excavating about 1,000,000 cubic yards). 

Potential exposure pathways, resulting from implementation 
of these alternatives, to residual contamination at KR 
include food chain or ingestion, direct contact and absorp- 
tion, and air migration and inhalation. Populations poten- 
tially exposed to contamination via these pathways include 
human populations (foragers, adjacent residents, workers and 



SAT74/38 S-1 



^ij 




hunters) and various fish and wildlife species. Insuffi- 
cient information exists to perform a quantitative risk as- 
sessment for potentially exposed human populations at KR. A 
qualitative risk assessment for human populations is pre- 
sented in the Kesterson Program EIS (USER, 1986a) . Food 
chain exposure is considered the most important exposure 
pathway for fish and wildlife at KR. 

Key fish and wildlife species were identified for quantita- 
tive risk assessment to represent the range of possible ex- 
posure impacts at KR. Selection of species was based on 
several considerations: they are the terminus of a major KR 
food chain exposure pathway, impacts on species have been 
observed in the past, they are rare or endangered species, 
they have particularly sensitive life stages, or information 
is available on the effects of selenium exposure for the 
species . 

Key species identified were the mallard, American coot, 
black-necked stilt, tricolored blackbird, mosquitof ish, 
eared grebe and San Joaquin Valley kit fox. These species 
represent potential exposure to contamination via the 
midwater, benthic, aquatic rooted plant, fish, and terres- 
trial pathways. Detailed food chain exposure diagrams for 
each of these species were abstracted into simplified 
selenium transfer models. These models were used with a 
"Monte Carlo" simulation technique to estimate the probabil- 
ity distribution of predictions of selenium concentration in 
the diets of the key species. 

Use of this modeling approach has several limitations. The 
model assumed a constant and steady state relationship be- 
tween selenium levels in exposure pathway components and 
does not take into account the length of time necessary to 
achieve steady state conditions. Also, because insufficient 
information exists to develop quantitative dose response 
relationships for diet selenium exposure for the key species 
at KR, the model results cannot be used to make quantitative 
estimates of the impact of cleanup alternatives on the ex- 
posed populations. 

A review of the toxicological effects of selenium indicates 
the following diet selenium concentrations may result in 
harmful impacts: 

Harmful Diet 

Diet Selenium Cleanup 

Key Species Concentration Goals 

Group (mg/kg) (mg/kg) 

Birds 5-10 3 

Mammals 2-5 — 

Fish 3-5 5 



SAT74/38 S-2 



These harmful effect ranges are different than cleanup goals 
because they represent the range of selenium concentrations 
where harmful effects have been observed rather than more 
conservative cleanup goals. 

The harmful effect levels and cleanup goals are compared to 
the model predictions of diet selenium levels to evaluate 
the potential for success of the alternative cleanup plans. 
Figures S-1 through S-3 and Table S-1 show the results. 

The risk characterization does not indicate that any of the 
plans will clearly fail. For avian species, the results for 
the FRP show that 40 to 65 percent of the diet selenium pre- 
dictions show levels below the harmful effect range. The 
Onsite Disposal Plan-1 shows a greater frequency of below 
harmful effect predictions, 65 to 90 percent. The Onsite 
Disposal Plan-2 results in the highest frequency of below 
harmful effect predictions, 85 to 95 percent. 

The risk characterization results show that each of the 
plans may present some risks to wildlife. Based on the 
methods and assumptions used for the risk characterization, 
predicted risks are greatest for the FRP, less for Onsite 1, 
and least for Onsite 2. 

Termination of drainwater flow and implementation of the FRP 
may reduce avian diet selenium concentrations to 8 mg/kg 
(below the top of the harmful effects range) at a relatively 
low first-year cost ($2.5 million); 50 percent of the diet 
selenium predictions indicate this result. Increased expen- 
ditures ($20 million in first-year costs) for the Onsite 
Disposal Plan-1 may reduce avian diet selenium concentrations 
to 4 mg/kg (below the bottom of the harmful effects range) , 
as indicated by 50 percent of the predictions. Greater ex- 
penditures ($40 million in first-year costs) for the Onsite 
Disposal Plan-2 may reduce avian diet selenium concentrations 
to 2.5 mg/kg (below the cleanup goal of 3 mg/kg) as indi- 
cated by 50 percent of the predictions. To achieve a 
greater probability (90 to 95 percent) that the cleanup 
goal of 3 mg/kg will be achieved, further excavation of KR 
would be necessary, at a cost of up to $144 million. 



SAT74/38 S-3 



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S-7 



Chapter 1 
APPROACH 



INTRODUCTION 



The overall objective of this risk assessment is to provide, 
to the extent feasible with existing information, a quantita- 
tive analysis of the magnitude and uncertainty of estimates 
of potential adverse impacts on fish, wildlife, and human 
populations that may result from implementation of Kesterson 
Reservoir (KR) cleanup alternatives. 

The risk assessment contains the following components: 

o Contamination evaluation and determination of con- 
taminants of concern 

o Analysis of exposure pathways, identification of 
key species, and estimates of transfer factors 
between pathway components 

o Review of toxicological properties of contaminants 
of concern for key species 

o Risk characterization, including the range of mag- 
nitude of expected exposure and the likelihood of 
such exposure occurring for each disposal alterna- 
tive 



CONTAMINATION EVALUATION 

The purpose of the contamination evaluation is to determine 
potential constituents of concern and the extent of their 
distribution at KR. Previous contamination evaluations for 
KR are reviewed and summarized. This evaluation includes a 
review of existing literature for evidence of the effects of 
contaminants at KR. 



EXPOSURE ASSESSMENT 

The objectives of this component are to identify the major 
contamination exposure pathways at KR; the key fish, wild- 
life, and human populations which are receptors of contami- 
nation from these pathways; the size of the exposed popu- 
lations; and to estimate transfer factors and their uncer- 
tainties, which describe contamination transport between 
exposure pathway components. 



SAT72/25 1-1 



I 



TOXICITY ASSESSMENT 

The objectives of the toxicity assessment are to determine 
the nature and extent of effects associated with exposure to 
contamination. It is a two-step process consisting of 
toxicological evaluation and dose-response assessment. 

The toxicological evaluation is a qualitative analysis of 
scientific data to determine the nature and severity of ac- 
tual or potential environmental risk associated with expo- 
sure to contamination. It results in a toxicity profile 
which presents a review of the literature on the types of 
adverse effects manifested, the doses employed, and the 
routes of exposure. 

The dose-response assessment is an attempt to make a quanti- 
tative estimate of impact from exposure to a toxic chemical. 
It defines the relationship between the dose of a chemical 
and the expected incidence of the adverse effect. 



RISK CHARACTERIZATION 

Risk characterization is the process of estimating the po- 
tential adverse environmental effect, using the results of 
the toxicity assessment, under the various conditions of 
exposure defined in the exposure assessment. 

Uncertainty related to the variability of bioaccumulation 
relationships and diet distribution are evaluated using a 
Monte Carlo simulation procedure. 

This procedure allows: 

o Estimation of the expected range of exposure levels 
given the variability of environmental conditions 
and the uncertainty of transfer and diet factors 

o Evaluation of the conceptual exposure pathway model 
regarding error due to poor estimates of input 
parameters, as well as the sensitivity of the model 
to particular parameters 

The Monte Carlo simulation procedure provides estimates of 
the range of predictions of contaminant exposure for each of 
the key species and cleanup alternatives. 



SAT72/25 1-2 



Chapter 2 
CONTAMINATION EVALUATION 



INTRODUCTION 



The source of contamination at KR is subsurface drainwater 
from irrigated agricultural lands that was delivered to KR 
via the San Luis Drain (SLD) . Delivery of drainwater ceased 
in June 1986. Contamination which remains at KR is that 
portion of contaminants delivered via drainwater that has 
accumulated in soils and biota. It is also possible that 
contaminants that have seeped into the shallow groundwater 
beneath KR could be reapplied to the surface of KR as part 
of water supply for the Flexible Response Plan (FRP) cleanup 
alternative (see Chapter 3) . 

The California State Water Resources Control Board (SWRCB) 
has identified constituents of concern in agricultural drain- 
water (SWRCB 1986) . These constituents are shown in Table 2-1 
and are used as a basis for further evaluation of KR contam- 
inants. The levels of these contaminants in SLD drainwater, 
KR surface water, KR groundwater, KR soils, and biota are 
evaluated to determine if there is any evidence for residual 
contamination that has accumulated in KR soils, biota, or 
groundwater that may result in future harmful effects to 
potentially exposed populations. 



PAST WATER CONTAMINANT CONCENTRATIONS 

Table 2-1 summarizes water quality guidelines and criteria 
established for the SWRCB constituents of concern (USBR 1986a) 
Table 2-2 is a summary of SLD drainwater quality during 1984 
and 1985 (USBR 1985). Table 2-3 summarizes KR surface water 
quality during 1984 and 1985 (USBR 1985) . Table 2-4 shows 
KR shallow groundwater quality during 1984 and 1985 (USBR 
1986a). The following drainwater constituents have exceeded 
water quality guidelines and criteria in historic SLD drain- 
water and KR surface water, and therefore warrant further 
analysis: boron, chromium, molybdenum, mercury, TDS, sele- 
nium, and zinc. 

BORON 

Boron was present in agricultural drainwater delivered to KR 
at concentrations ranging from 13,000 to 17,000 yg/l while 
boron concentrations in the surface water at KR have been in 
range of 11,000 to 65,000 yg/l. These data show that boron 
levels increased in some areas probably due to evaporation 
in KR surface water. 



SAT72/35 2-1 





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cNoix>r-^rH(Tim(Nnr-or^'3' 

rHmrN)(Nr\)(NrH(NrH<NrHrO(N(N 

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2-6 



I 
I 



Table 2-4 
KESTERSON RESERVOIR SHALLOW GROUNDWATER 
CONSTITUENTS OF CONCERN 
(1984-1985) 

Monitoring Data (yjg/l) 







USBR Monitoring 


Well 


Data 








March 1984 - 


November 


1985 




Constituent 


Background Wells 


Kc 


;sterson 
3. Obser. 

655 


Re 


;servoir 


(yg/1) 


No. Obser. Average 
56 3,076 


Nc 


Average 


Boron 


14,000 


Cadmium 


55 


1.1 




599 






1.3 


Chromium 


58 


5.8 




651 






9.5 


Copper 


49 


3.3 




581 






9.9 


Mercury 


51 


0.11 




610 






0.13 


Manganese 
















Molybdenum 


54 


14.2 




657 






59.2 


Nickel 


56 


10.6 




647 






30.3 


Selenium 


60 


1.8 




817 






9 


Zinc 

TDS° (mg/1) 


32 


56.5 




453 






78 


62 


4,000 




883 






10,900 



Values less than detection limit set equal to detection 
limit to calculate averages. Data for steel-cased wells 
are not included for zinc. 

TDS for monitoring wells estimated by multiplying electrocon- 
ductivity by 0.8. 



SAT72/74 



2-7 



I 
I 
I 
I 
I 
I 
I 
I 



Concentrations of boron in the shallow groundwater beneath 
KR average 14,000 yg/l or about the same concentrations as 
in the surface water. 

CHROMIUM 

Agricultural drainwater delivered to KR contained 4 to 30 ug/l 
of chromium. KR surface water samples showed levels from 
less than 1 to 19 yg/1. The difference in concentrations 
between SLD drainwater and KR surface water indicates that 
chromium may be removed from the water column. The concen- 
trations of chromium in the shallow groundwater beneath KR 
are approximately equal to surface water at KR, showing that 
chromium is not removed from water as it seeps through the 
soil into the ground. 

MERCURY 

Levels of mercury in drainwater varied from less than 0.1 to 
3 yg/1. Levels up to 0.6 yg/1 have been found in KR surface 
water. The level of mercury in shallow groundwater beneath 
KR was 0.13 yg/l, approximately equal to background 
concentrations of 0.11 yg/l. 

MOLYBDENUM 

Molybdenum in SLD water delivered to KR ranged from 28 to 
140 pg/1. Surface water molybdenum concentrations at KR 
ranged from 48 to 540 yg/1, indicating molybdenum concen- 
trations increased probably due to evaporation in KR surface 
water. Molybdenum concentrations in groundwater beneath KR 
is lower than KR surface water, indicating that molybdenum 
may have been removed in soil as surface water seeped into 
the ground. 

SALTS 

Agricultural drainwater delivered to KR contained 4,992 to 
10,896 mg/1 of total dissolved solids (TDS) . Surface water 
samples from ponds at KR showed TDS levels 1,272 to 
16,880 mg/1, indicating an increase in concentrations pro- 
bably due to evaporation. 

SELENIUM 

Levels of selenium in SLD drainwater averaged approximately 
300 yg/1. 

Levels of selenium in KR surface water decreased from south 
to north, suggesting that selenium was removed from the water 
column, probably by chemical or biological processes (LBL, 
1986) . 

Selenium concentrations in the shallow groundwater beneath 
KR are much lower than in KR surface water, also suggesting 
selenium is being removed in KR soils and sediments. 

SAT72/35 2-8 



ZINC 

Concentrations of zinc in the shallow groundwater beneath KR 
are similar to those historically found in KR surface water, 
suggesting that zinc has seeped into the groundwater and has 
not accumulated in KR soils. 



PRESENT SOIL AND WATER SUPPLY 
CONTAMINANT CONCENTRATIONS 

Table 2-5 shows constituents of concern levels in KR soils 
(USER 1986a) . No nearby KR wetland soil background levels 
for these contaminants, except for selenium, have been iden- 
tified. Table 2-5 also shows expected constituent concen- 
tration in San Joaquin Valley soils similar to those under- 
lying KR. Selenium is the only constituent which exceeds 
either background levels or San Joaquin Valley soils levels. 

Table 2-6 shows the quality of groundwater based on analyses 
of existing water supply which will be applied to KR with 
implementation of FRP . Boron and TDS (0.8 x EC) are the 
constituents of concern which exceed water quality guide- 
lines and criteria. 



BIOTA 

BACKGROUND 

Mosquitofish (Gambusia af finis ) captured at KR in May 1982 
were found to have high levels of selenium (about 135 ppm - 
Saiki 1986). Because of these findings, the U.S. Fish and 
Wildlife Service (USFWS) began intensive studies at KR and 
at Volta Wildlife Area (a control area 10 km to the south- 
west which receives surface water) to further define the 
effects and extent of contamination resulting from drain- 
water application to KR. 

In 1983, samples collected by USFWS included tissues and 
eggs of American coots, ducks, eared grebes ( Podiceps 
nigricallis ) , and black-necked stilts ( Himantopus mexicanus ) . 
These samples were analyzed for selenium, arsenic, cadmium, 
mercury, lead, zinc, and silver. Elements other than selenium 
were found in similar concentrations in the samples from KR 
and the Volta control site. Samples of food chain compo- 
nents, including rooted plants, invertebrates, and mosquito- 
fish, were also collected at both sites in 1983. These 
samples were analyzed for silver, arsenic, boron, cadmium, 
chromium, copper, mercury, molybdenum, nickel, lead, sele- 
nium, and zinc. Only total selenium and boron concentra- 
tions were significantly higher in food chain samples 
collected at KR than in those collected at Volta Wildlife 
Area (Ohlendorf , et al. 1986) . 



SAT72/35 2-9 



Table 2-5 

SUMMARY OF SOIL CONCENTRATIONS (MG/KG) OF 

CONSTITUENTS OF CONCERN 



San Joaquin Valley 
Background Soils 



Kesterson Soil' 
and Sediments 



Constituent 


Min. 
NDA 


Max. 
NDA 


Mean 
NDA 


Min. 
LD 


Max. 
LD 


Mean 


Boron 


LD 


Cadmium 


LD 


2 


2 


LD 


LD 


LD 


Chromium 


LD 


770 


66 


25 


160 


53 


Copper 


LD 


160 


23 


4 


33 


14 


Manganese 


LD 


2,300 


660 


210 


880*^ 


434 


Mercury 


LD 


9.4 


.07 


LD 


LD 


LD 


Molybdenum 


LD 


28 


2.1 


LD 


10 


3 


Nickel 


LD 


160 


37 


9 


120 


34 


Selenium 


LD 


2.8 


.24 


LD 


85 


7 


Zinc 


LD 


140 


70 


13 


loo'^ 


NDA 



Ron Tidball, USGS, unpublished data. 

USER (1986a) 

c 
One sample out of 157 had 2,600 mg/kg Mn. 

d 
One sample had 220 mg/kg and one sample had 230 mg/kg out of 157 samples. 

Notes: LD = Less than analytical detection limit. 

NDA = No data available. 

Means calculated not including values less than detection. 



SAT72/73 



2-10 



I 
I 
I 
I 



Table 2-6 
QUALITY OF GROUNDWATER TO BE APPLIED TO KESTERSON RESERVOIR UNDER FRP 



Site 

Name 

Well #1 
Well #1 
Well #1 
Well #1 
Well #1 
Well #1 
Well #2 
Well #2 
Well #2 
Well #2 
Well #3 
Well #3 
Well #3 
Well #3 
Well #3 
Well #4 
Well #4 
Well #4 
Well #4 
Well #4 
Well #4 
Well #5 
Well #6 
Well #7 
Well #8 



Date 
Sampled 

07/09/86 
07/15/86 
07/24/86 
07/31/86 
08/06/86 
09/29/86 
07/09/86 
07/15/86 
07/24/86 
09/29/86 
07/09/86 
07/15/86 
07/24/86 
08/06/86 
09/29/86 
07/09/86 
07/15/86 
07/24/86 
07/31/86 
08/06/86 
09/29/86 
09/29/86 
09/29/86 
09/29/86 
09/29/86 



EC 
Umbos /cm 

10160 

10600 

10940 

11320 

11290 

11790 
6210 
5820 
6000 
6160 
4830 
4850 
4990 
5150 
6250 
6140 
6170 
6350 
6520 
6530 
5280 
6670 
5320 
6320 
7460 



As Se Cr Cu Mo Ni Zn B Ca Mg 
yg/L yg/L yg/L yg/L yg/L yg/L yg/L yg/L Mg/L Mg/L 

1 yt -3 /A 1/1 yi /•in Annn lAn •jin 



14 
16 
24 
20 
24 
21 
5 
7 
9 
8 
<4 
<4 
<4 
24 
14 
12 
12 
11 
12 
14 
<4 
11 
6 
13 
10 



<10 
<10 
<10 
<10 
<10 
<10 
<10 
<10 
<10 
<10 
<10 
<10 
<10 
<10 
<10 
<10 
<10 
<10 
<10 
<10 
<10 
<10 
<10 
<10 
10 



4000 340 
4000 

5000 370 

5000 360 

5000 360 

6000 370 

1900 200 
1800 

2000 200 

1500 200 

700 250 

800 

800 160 

800 160 

1700 190 

1800 190 

200 

2000 210 

2000 210 

2000 210 

800 170 

2200 230 

1000 150 

2100 190 

2800 250 



310 

340 
330 
330 
340 
160 

160 
160 
120 

130 
130 
140 
140 

160 
150 
160 
36 
160 
120 
140 
190 



SAT 73/ 76 



2-11 



Boron found in vegetation at KR tends to concentrate in leaf 
tips where it is available to browsing animals (Gupta et al. 
1985) . Few data are available, however, concerning the acute 
and chronic toxicity of boron to fish and wildlife. Boron 
compounds (boric acid and borax) have been shown to cause 
mortality and teratogenic development when injected into 
eggs (Landauer 1952, Birge and Black 1977). 

In 1983, researchers concluded that selenium was the most 
likely cause of avian deaths and deformities at KR because 
the types of deformities found in avian embryos and young 
were typical of those induced by exposure to high levels of 
selenium, and selenium concentrations in the samples greatly 
exceeded those found in other areas of the United States 
(USDI 1984) . Thus, selenium has been identified as the prin- 
cipal contaminant of concern at KR. 

The importance of selenium as a contaminant at KR is increas- 
ed because of the likelihood of bioaccumulation . Studies by 
Lemly (1985) in an aquatic ecosystem indicated that plankton 
(zooplankton and phytoplankton combined) concentrated selenium 
to 750 times the concentration in the water of Belews Lake, 
North Carolina, and that fish contained selenium concentrations 
4,000 times that in water. In addition, sediments contained 
350 times and benthic invertebrates contained 1,050 times 
the selenium concentrations of water in the lake. Selenium 
in water is taken up by biota including marsh plants, phyto- 
plankton, zooplankton, and insects that contribute to the 
diets of higher forms of wildlife in the area (Burau 1985) . 
Bioaccumulation has also been documented at KR (Ohlendorf, 
et al. 1986) . 

INVERTEBRATES 

Data on concentrations of selenium in invertebrates at KR 
show levels 12 to 130 times as contaminated as those col- 
lected at Volta Wildlife Area during the same period 
(Table 2-7) . More recent data on selenium concentrations in 
invertebrates from KR and vicinity are available in a recent 
Lawrence Berkeley Laboratory report (LBL 1986) . These data 
are used in the Exposure Assessment section of this report. 

BIRDS 

Ohlendorf, et al. (in press) found reproductive problems in 
aquatic birds nesting at KR in 1983-1985. Samples of bird 
eggs and livers collected at KR contained elevated levels of 
selenium. According to Ohlendorf (pers. comm.), selenium 
concentrations in livers of American coots collected in 1984 
from KR contained almost twice the mean concentrations of 
selenium found in livers of coots collected at KR in 1983 
(81.5 and 43.1 mg/kg, dry weight, respectively). Selenium 
concentrations in livers of ducks collected at KR in 1983 
averaged 19.9 mg/kg dry weight (Presser and Ohlendorf in 
prep.). In areas without selenium contamination, dry 

SAT72/35 2-12 



Table 2-7 

SELENIUM CONCENTRATION (PPM DRY WEIGHT) IN 

COMPOSITE SAMPLES OF INVERTEBRATES, MAY 19 83 

Volta Wildlife Area Kesterson Reservoir 



Sample N_ Mean (Range) N Mean (Range) 

Water boatmen 

(Corixidae) 5/5 1.91 (1.1-2.5) 2/2 22.1 (20-24) 

Midge larvae 

(Chironomidae) 3/3 2.09 (1.5-3.0) 3/3 139 (71-200) 

Dragonfly nymphs 

(Anisoptera) 2/2 1.29 (1.2-1.4) 6/6 122 (66-179) 

Damselfly nymphs 

(Zygoptera) 2/2 1.45 (1.2-1.7) 3/3 175 (119-218) 



Number with measurable concentrations/number analyzed. 

Geometric means, computed only when selenium was measurable 
in at least 50 percent of samples. 

Source: Modified from Ohlendorf et al. (in press a) . 



SAT72/36 

2-13 



I 
I 



weight concentrations are usually less than 1 mg/kg in eggs, 
and less than 10 mg/kg in livers of freshwater birds 
(Ohlendorf pers. comm.). 

Data available on the rates of embryonic mortality and de- 
formity during the 1985 breeding season at KR (Table 2-8) 
indicated that of 124 nests monitored, 39.5 percent contain- 
ed at least one dead or deformed embryo (Ohlendorf pers. 
comm.). The 1985 data indicated that nesting failures and 
high rates of embryotoxicity continued to occur, despite an 
active hazing program in 1985. In contrast, researchers 
found no abnormalities in embryos from nests monitored through 
late stages of incubation or hatching at Volta Wildlife Area 
in 1983-1985. Nests studied included those of pied-billed 
grebes ( Podilymbus podiceps ) , killdeer ( Charadrius vociferus ) , 
mallards (Anas platyrhynchos ) , northern pintails (A^ acuta) , 
gadwalls (A_^ strepera ) , cinnamon teal (A_^ cyanoptera ) , Amer- 
ican coots ( Fulica americana ) , black-necked stilts ( Himaatopus 
mexicanus) , American avocets ( Recurvirostra americana ) , and 
eared grebes ( Podiceps nigricollis ) . 

The expected incidence of major external malformations in 
hatchlings of uncontaminated wild populations of birds and 
in embryos of laboratory-incubated mallard eggs is less than 
one percent (Pomeroy 1962, Gilbertson, et al. 1976, Hoffman 
1978, Hill and Hoffman 1984). 

Studies by Heinz, et al. (in press) indicated that when mal- 
lards were fed diets containing 10 mg/kg selenium as seleno- 
methionine, some embryos had deformities similar to those 
observed at KR. Selenium concentrations in eggs of aquatic 
birds at KR were far higher than those at the Volta Wildlife 
Area which served as a control. 

In 1983, only a few young were observed from the presumed 

2 58 coot eggs hatched at Kesterson NWR, and only one young 
eared grebe was observed of the presumed 211 eggs hatched 

(Ohlendorf et al. 1986) . The number of young coots surviv- 
ing to adulthood is unknown. Despite thorough searches, no 
coot broods were observed, although coot and grebe broods 
were observed at Volta Wildlife Area. No coots nested at KR 
in 1984 or 1985 (Ohlendorf pers. comm.). 

In 1984, no American avocet or black-necked stilt broods 
were observed past 2.5 weeks of age at KR (Niesen and 
Williams 1985). In 1985, no American avocet hatchlings over 

3 weeks of age were observed at KR. Avocet and stilt hatch- 
lings up to 6 weeks of age were observed at Volta Wildlife 
Area. No survival of juvenile avocets or stilts was record- 
ed at KR, while recruitment of juvenile avocets and stilts 
into the adult populations appeared normal at Volta Wildlife 
Area in 1984 and 1985. In addition, more hatchling carcas- 
ses were found at KR in 1985 than in 1984 (Niesen and Williams 
1985) . 

SAT72/35 2-14 



I 



Table 2-8 

SUMMARY OF FREQUENCIES OF MORTALITY AND DEFORMITIES IN 

EMBRYOS AND CHICKS OF AQUATIC BIRDS NESTING AT 

KESTERSON RESERVOIR, 1983-85 

Nests with Embryotoxicity 



Species/ 


Nests^ 
59/91 




Dead 


De 


iformed 




Total 


Year 


No. 
35 


Percent 
(59.3) 


No. 
25 


Percent 
(42.4) 


No. 
38 


Percent 


Coot 
1983 


(64.4) 


Eared grebe 
1983 


141/163 


84 


(59.6) 


22 


(15.6) 


89 


(63.1) 


Stilt 
1983 
1984 
1985 


101/125 

63/189 

69/96 


17 

7 

20 


(16.8) 
(11.1) 
(29.0) 


18 
12 
23 


(17.8) 
(19.0) 
(33.3) 


24 
14 
30 


(23.8) 
(22.2) 
(43.5) 


Avocet 
1983 
1984 
1985 


16/16 
19/51 
22/35 




4 


(0) 
(0) 
(18.2) 




4 


(0) 
(0) 
(18.2) 




5 


(0) 
(0) 
(22.7) 


Killdeer 
1984 
1985 


12/32 
16/25 




7 


(0) 
(43.8) 



3 


(0) 
(18.8) 



8 


(0) 
(50.0) 


Ducks 
1983 
1984 
1985 


30/42 
13/36 
17/27 


5 
6 
6 


(16.7) 
(46.2) 
(35.3) 


3 

2 


(10.0) 

(0) 

(11.8) 


7 
6 
6 


(23.3) 
(46.2) 
(35.3) 



Monitored/found; nests monitored to hatching or from which 
a late-stage embryo was collected/nests found during study, 
including those lost to predation, flooding, desertion, etc, 

Dead = number of nests (and percent) with one or more dead 
embryos; deformed = nests with one or more deformed embryos 
or chicks; total = sum of all nests with at least one dead 
or deformed embryo or chick. All percentages calculated by 
dividing by number of "monitored" nests. 

Source: Ohlendorf (pers. comm. b) . 



SAT72/37 



2-15 



Selenium concentrations in duck muscle tissue from 1984 col- 
lections at Kesterson NWR by the California Department of 
Fish and Game ranged from 0.2-9.2 mg/kg wet weight (Daniel 
pars. comm.). Because of potential risks to human health 
from consuming foods with high selenium concentrations. De- 
partment of Health Services recommended that no waterfowl 
from Kesterson NWR be consumed (Kizer pers. comm.). Also, 
the USFWS has prohibited hunting and fishing at KR since 
1984. 

MAMMALS 

A study of potential selenium contamination of mammals at KR 
was conducted in 1984. Species collected at KR and at Volta 
Wildlife Area included the California vole ( Microtus 
californicus ) , harvest mouse ( Reithrodontomys megalotis ) , 
house mouse (Mus musculus ) , ornate shrew ( Sorex ornatus ) , 
desert cottontail ( Sylvilagus auduboni) , California ground 
squirrel ( Citellus beecheyi ) , and muskrat ( Ondatra zibethica ) . 
Preliminary results are reported below. 

Reproductive problems were noted for California voles and 
house mice at KR, but not at Volta Wildlife Area. Western 
harvest mice and ornate shrews showed reproductive activity 
at KR, but a comparison with a control area could not be 
made since no females of either species were caught at Volta 
Wildlife Area (Clark pers. comm.). 

Selenium concentrations were higher than background in the 
livers of specimens from KR for all species except the 
California ground squirrel (Clark pers. comm.). Preliminary 
data for the four most abundant species in this sample 
(California vole, harvest mouse, house mouse, and ornate 
shrew) are presented in Table 2-9; for these species, sele- 
nium levels at KR were 10 to 1,000 times higher than those 
at the Volta Wildlife Area. Livers from the carnivorous 
ornate shrews averaged 6 times more selenium than harvest 
mouse livers and 22 times more than California vole livers. 
The mean body burden of these species of herbivores (Cali- 
fornia vole, house mouse, and harvested mouse) shows a sele- 
nium level of 8.18 mg/kg. The single sample of ornate shrew, 
a small carnivorous rodent, had a body burden of 47.9 mg/kg, 
or about 6 times higher than found in herbivorous rodents of 
a similar size. Larger rodents, California ground squirrel 
and muskrat, had generally lower liver tissue selenium than 
observed in small rodents. 

HUMAN POPULATIONS 

The Merced County Health Department conducted a limited public 
health survey of persons living directly adjacent to KR compar- 
ed to a control group from Gustine. This survey included a 
questionnaire and blood, urine, and hair analyses. Based on 
the limited amount of human toxicological information 



SAT72/35 2-16 



Table 2-9 

SELENIUM CONCENTRATIONS (PPM DRY WEIGHT) IN 

LIVERS AND WHOLE BODIES OF ABUNDANT SMALL MAMMAL SPECIES FROM 

KESTERSON RESERVOIR AND VOLTA WILDLIFE AREA (PRELIMINARY DATA) 



Volta Wildlife Area 



Kesterson Reservoir 







Liver 


(Rang 


le) 




Liver 


(Range) 


N_ 


Whole Bodies 


Species 


Pond 


N 


Mean" 


Pond 


N_ 


Mean 


Mean (Range) 


California 
vole 


5 
7 


5 
5 


0.228 
0.229 


(ND-1. 
(ND-1. 


4)^ 
2) 


2 
5 
7 

9 
11 


5 

14 

6 

2 

1 


119 

7.79 

4.29 

4.85 
9.2 


(61-250) 

(ND-38) 

(3.3-5.8) 

(4.8-4.9) 


2 
2 
1 


23 (13,33) 
2.4 (ND, 4.6) 
1.4 


Harvest 
mouse 


5 
7 


1 
4 


2.1 
1.69 


(1.2-2 


1.2) 


5 
6 
7 


5 
4 
2 


15.3 
38.2 
15.5 


(6.5-34) 

(19-73) 

(9.0-22) 


2 
1 


3.2 (2.4, 4.0) 
27 


House mouse 


5 


5 


2.67 


(1.9-3 


1.7) 


2 

5 


2 

5 


14.5 
4.17 


(11-18) 
(ND-41) 


2 


18.1 (82,28) 


Ornate shrew 


This single shrew from 
Volta Wildlife Area was 
not analyzed 




7 
11 


8 

1 


92.7 
100 


(13-210) 


4 


47.9 (10-100) 


Muskrat 


6 

10 
12 
13 

14 


1 
1 
1 
3 
1 


ND 

1.5 

0.82 

0.351 

1.9 


(ND-0. 


96) 


Drain 

3 

11 


1 
3 

1 


1.7 

32.1 

2.5 


(18-92) 






California 

Ground 

Squirrel 


4 

12 
13 


1 
1 
1 


0.58 
0.93 
1.1 






8 
11 


2 

1 


1.82 
0.81 


(0.73, 2.9) 




Cottontail"^ 
Rabbit 


1 
5 


1 
1 


0.14 
0.13 






9 

10 


1 
2 


2.1 
2.2 


(1.1, 3.3) 







Tteans are geometric for samples of N>2 because of skewness 
in the data. ND values are entered at 0.1 ppm, which is 
the detection limit. 

Selenium not detected. 

Entire animal minus stomach contents. 

Tliigh muscle only. 

Source: Clark (pers. comm.). 



Whole bodies not analyzed for Volta. 



SAT72/39 



2-17 



I 
I 
I 



available for selenium, no evidence was found to indicate 
acute toxic effects on area residents resulting from expo- 
sure to KR (Merced County Health Department 1985). 

A public health selenium monitoring program for workers at 
KR was instituted at KR in 1984. From October 1984 to the 
present, blood chemistry and blood and urine selenium analy- 
ses were performed. Symptoms of acute or chronic selenium 
toxicity were not observed, and serum and urine selenium 
levels are within normal ranges (USER 1986b) . 



IDENTIFICATION OF CONSTITUENTS FOR RISK CHARACTERIZATION 

Table 2-10 summarizes the results of the foregoing analyses. 
Based on this table, only boron and selenium are of potential 
concern with regards to this Risk Assessment. The following 
constituents are not of concern because they have not exceeded 
standards or guidelines in past measurements of SLD drainwater, 
KR surface water, and KR groundwater: cadmium, copper, man- 
ganese, and nickel. The following constituents are not of 
concern because they have not accumulated in KR soils above 
background concentration, and their concentrations in KR 
groundwater supplies do not exceed standards or guidelines: 
chromium, mercury, molybdenum, and zinc. TDS is not of con- 
cern, even though concentrations in KR groundwater supplies 
exceed standards and guidelines, because no evidence exists 
that TDS concentrations in applied groundwater will cause 
adverse wildlife effects in KR. 

Boron is an essential nutrient for plants in low concentra- 
tions and exhibits toxic affects at higher levels. Reviews 
of boron nutritional requirements (Gupta, et al. 1985) and 
toxicity (Maas 1986) have been summarized by USER (1986a). 
Typically, plants will exhibit toxic effects when, depending 
upon their tolerance, the boron concentrations exceed 
200 mg/kg. However, many intolerant species of plants are 
affected by much lower levels of boron (5 to 50 mg/kg) . 
Boron is accumulated in plant tissues at variable rates 
dependent upon species metabolism, soil, water, transpira- 
tion, and other variable environmental factors (Gupta, et 
al. 1985, Maas 1986, USER 1986a). 

Analytical results from 350 stem and leaf tissue samples of 
vegetation collected at KR had leaf tissue concentrations 
ranging from 10 to 610 mg/kg boron, with an average of 
174 mg/kg (USER 1986a) . Boron levels exceeded 200 mg/kg in 
36 percent of the plant samples, which represented all ponds 
at KR. 



SAT72/35 2-11 



I 



I 



I 



Table 2-10 
SU^4MARY OF CONTAMINANT LEVELS IN KR MEDIA 



Drainwater, 
Surface Water, 

or Shallow KR Water Supply 

Groundwater > KR Soils > Groundwater KR Biota 
Cons tituents Standards? Background? > Standards? > Background? 

Yes Yes 



No No 



No No 

No No 

No Yes 

No No 

Yes NA 



Boron 


Yes 


No 


Cadmium 


No 


~ 


Chromium 


Yes 


No 


Copper 


No 


— 


Manganese 


No 


~ 


Mercury 


Yes 


No 


Molybdenum 


Yes 


No 


Nickel 


No 


— 


Selenium 


Yes 


Yes 


Zinc 


Yes 


No 


TDS 


Yes 


NA 



Note: NA = Not applicable. 



SAT74/65 



2-19 



I 
I 
I 
I 
I 
I 
I 
I 
I 



In a 1983 study of trace element concentrations in rooted 
plant leaf tissues, Ohlendorf, et al. (1986a) compared 
samples from sites exposed to drainwater at KR to a control 
site at Volta Wildlife Management Area. The results showed 
boron in one plant sample from the Volta area contained 
34 mg/kg dry weight, while 9 samples taken at KR ranged from 
270 to 510 mg/kg (mean = 382 mg/kg) or more than 10 times 
the level of the control site. Aquatic insect samples taken 
at KR had a mean of 45.2 mg/kg boron (range 36-54 mg/kg), 
while samples from Volta contained 13.4 mg/kg (range 
6.7-35 mg/kg). Similarly, mosquitofish at KR had a mean 
tissue boron level of 11.1 mg/kg (range 8.0-20 mg/kg), while 
Volta samples showed a level of only 2.75 mg/kg (range 
ND-3.6 mg/kg). The exposure of the KR food chain to high 
levels of boron in drainwater has resulted in apparently 
higher levels in the organisms investigated thus far. 

The implications of the available data are difficult to in- 
terpret given the present state of knowledge for several 
reasons. First, no data are available that indicate the 
dietary intake of boron by higher food chain components such 
as birds or carnivores. Secondly, little information is 
available that indicates potential toxic effects of boron in 
wildlife species. 

Sax (1984) reports an oral-LD50 for mice of 2,000 mg/kg as 
boric acid. Limited acute aquatic toxicity data for mosquito- 
fish indicate that relatively high boron concentrations are 
needed to achieve a lethal dose. Boron concentrations rang- 
ing from 3,600 to 5,600 mg/1 (sodium borate and boric acid, 
respectively) have been reported as being toxic (SWRCB 1963) . 
Acute and chronic toxic effects of boron in the diet of wild 
birds or mammals has not been reported in the literature. 
Further studies are needed to determine whether ingested 
boron adversely affects wildlife reproduction (SWRCB 1986) . 
Also, because of the mobility of boron, it is expected that 
boron presently accumulated in KR vegetation will not remain 
in the KR ecosystem although it may be reapplied as part of 
the water under the FRP . 

Boron is not evaluated further in this Risk Assessment be- 
cause, as discussed above, there is no existing evidence 
linking boron to observed KR wildlife effects; evidence does 
exist for selenium. Further study of the potential toxic 
effects of boron on wildlife species does, however, appear 
warranted. If such studies do link boron to wildlife toxi- 
city, then risks to wildlife would be greater for the FRP 
than for the Onsite Disposal Plans, since the FRP includes 
using high boron local groundwater as a KR water supply (see 
Chapter 3) . 



SAT72/35 2-20 



Chapter 3 
EXPOSURE ASSESSMENT 



INTRODUCTION 



Risk assessment requires estimating selenium exposure that 
may occur as a result of implementing each of the several KR 
cleanup alternatives. 

This section presents a description of the cleanup alterna- 
tives being considered for KR, a description of the biogeo- 
chemistry of selenium, a description of potential major 
selenium exposure pathways resulting from these cleanup 
alternatives, an identification of key species which are 
potential receptors of contamination from these pathways, 
the population sizes of the key species, a description of 
exposure pathway components, an estimate of selenium trans- 
fer factors (and their uncertainties) between pathway com- 
ponents, and key species diet factors. 



CLEANUP ALTERNATIVES 

Cleanup alternatives under consideration for implementation 
at KR were developed and qualitatively evaluated in the 
Kesterson Program EIS (USER 1986a). These alternatives are: 
the Phased Approach, the Onsite Disposal Plan, and the Off- 
site Disposal Plan. For the purposes of this risk assess- 
ment, it is necessary to consider components and subalterna- 
tives of these plans. 

PHASED APPROACH 

The phased approach consists of three components: the Flex- 
ible Response Plan (FRP) , the Immobilization Plan, and the 
Onsite Disposal Plan. 

Flexible Response Plan 

Under the FRP, the southern ponds (Ponds 1-8) where most of 
the soil selenium contamination occurs would be flooded with 
low selenium groundwater, and the northern ponds (Ponds 9-12) 
would not have water applied. Vegetation in the northern 
ponds would be controlled by discing. Some areas of the 
northern ponds could be seasonally wet when groundwater rises 
typically November through April. 

Immobilization Plan 

The Immobilization Plan is similar to the FRP to the extent 
that water would continue to be applied to the southern 
ponds and the northern ponds would not have applied water. 



SAT72/77 3-1 



Emergent vegetation in the southern ponds would be harvested 
and disposed off site. In the northern ponds, exposure to 
contamination would be controlled through discing, and if 
necessary, vegetation harvesting and offsite disposal, or 
filling seasonal wetlands with soil. These management 
actions will reduce risk to wildlife compared to the FRP . 
Contamination exposure in the northern ponds under the Im- 
mobilization Plan is expected to be between that resulting 
from the FRP and the Onsite Disposal Plan. The Immobiliza- 
tion Plan is therefore not considered further in this risk 
assessment. Because insufficient information currently ex- 
ists regarding the magnitude of reduced risks to wildlife 
achievable with this plan, the immobilization plan will be 
tested as part of the FRP. 

Onsite Disposal Plan 

Under the Onsite Disposal Plan, contaminated soils and 
vegetation would be excavated and disposed of onsite in a 
lined and capped landfill. This plan has two subalterna- 
tives: excavating KR soil with selenium levels greater than 
4 mg/kg and harvesting all above-ground vegetation (approxi- 
mately 450,000 cubic yards) (Onsite-1) and excavating all KR 
soil and vegetation (approximately 1,000,000 cubic yards) 
(Onsite-2) . These alternatives are addressed in this risk 
assessment. 

ONSITE DISPOSAL PLAN 

Under this plan, onsite disposal (either 450,000 or 
1,000,000 cubic yards) would be implemented immediately 
rather than as the third component of the phased approach. 
Since the risk assessment does not consider the time frame 
of plan implementation, the risks of this plan are essen- 
tially identical to the phased approach onsite disposal 
plan. 

OFFSITE DISPOSAL PLAN 

This plan is similar to the Onsite Disposal Plan with the 
exception that excavated and harvested material would be 
disposed of offsite rather than onsite. Since the risks of 
landfill failure are not being considered, the risks of this 
plan are essentially identical to the phased approach onsite 
disposal plan. 



SELENIUM BIOGEOCHEMISTRY 

The major features of selenium chemistry that affect its 
movement and toxicity are associated with changes in its 
oxidation state and the resulting differences in chemical 
properties . 



SAT72/77 3-2 



I 

■ 



Selenate is the most mobile form of selenium and makes up 
the majority of selenium that has been delivered to KR via 
the SLD. Selenium was removed from the drainwater applied 
to KR, apparently by biological processes, and also from the 
water as it seeped into the groundwater through the anaerobic 
sediments, probably by both chemical and biological pro- 
cesses. This selenium which has accumulated in the soils 
and sediments of KR is in reduced inorganic forms, such as 
selenite and elemental selenium, and in organic selenium 
compounds. This accumulated selenium can potentially be 
mobilized into overlying water by physical, chemical, and 
biological processes and hence again become bioavailable or 
may be transported through the food chain via the detritus 
pathway. 

EXPOSURE PATHWAYS 

Potential exposure pathways to residual selenium contamina- 
tion at KR include food chain or ingestion of contaminated 
sediments, water, plants, and animals, direct contact and 
dermal absorption, and air migration and inhalation. All of 
these are possible pathways for potentially exposed human 
populations . 

Food chain exposure is considered the most significant expo- 
sure pathway for wildlife at KR. No information reviewed 
suggests that dermal exposure or inhalation is a significant 
exposure pathway for selenium at KR. Fish, however, are 
directly affected by selenium in the water column but sele- 
nium concentrations in surface water under all plans are 
expected to be below the EPA criterion to protect aquatic 
life (see Chapter 4) . 

The fish and wildlife food chain exposure pathways can be 
divided into subpathways which relate to the properties and 
movement of selenium. As described in the Kesterson Program 
Final EIS (USER 1986) , the potential exists for residual 
soil selenium contamination to move into terrestrial and 
aquatic food chains. The terrestrial food chain represents 
the dry areas of KR after implementation of a cleanup al- 
ternative (e.g., dry areas of northern ponds under FRP) . 
The aquatic food chain represents either the permanently wet 
areas (e.g., the southern pond under FRP) or the seasonably 
wet areas (e.g., the low areas of the northern ponds under 
the FRP and the low areas of all the ponds under the Onsite 
Disposal Plan) . The aquatic food chain is further divided 
into a benthic pathway, a water column pathway, and a rooted 
plant pathway. 



SAT72/77 3-3 



I 



EXPOSED POPULATIONS 

HUMAN POPULATIONS 

Insufficient information exists to perform a quantitative 
risk assessment for potentially exposed human populations at 
KR. The Kesterson Program Final EIS (USER 1986a) presents a 
thorough, comprehensive analysis of exposure of human popu- 
lations to KR contaminants, based on the most recent data 
available. Potentially exposed populations are described 
below. 

Foragers 

There is a lack of data on the potentially exposed popula- 
tion, such as estimates of the population size, frequency of 
their use of the area, their dietary habits in general, what 
items at KR they may consume, their normal dietary intake of 
selenium, the selenium concentrations of some potential food 
items, or the amount of food or other contaminated media 
they may take in. A preliminary ethnographic survey has 
been recently completed (USER, 1986c) , but further informa- 
tion would be necessary to allow quantitative risk assess- 
ment. 

Adjacent Residents 

Groundwater exposure is expected to be minimal due to limit- 
ed selenium migration in the groundwater (USER 1986a, LBL 
1986) and lack of groundwater beneficial use as described in 
the Kesterson Program Final EIS (USER 1986a) . 

Workers 

Each alternative has a different exposed population. They 
include the normal Kesterson workers and researchers, but 
excavation would also include construction workers. 

Hunters 

Hunting is not allowed at KR. There is no information 
available on the fraction of total diet that comes from KR 
of the birds shot at adjacent duck clubs or other offsite 
areas . 

WILDLIFE POPULATIONS 

A list of species present at KR is given in Appendix A and 
is based on USER (1986a) . The species at KR represent a 
variety of trophic levels and, hence, selenium exposure po- 
tential. Criteria for selection of species for risk charac- 
terization are described below. 



SAT72/77 3-4 



IDENTIFICATION OF KEY FISH AND WILDLIFE SPECIES 

Appendix A presents a list of wildlife species known or sus- 
pected to use KR. It was not possible to perform a quanti- 
tative risk assessment for each of these species due to time 
and budget constraints. However, it is not necessary to 
perform a risk assessment for each of these species because 
indicator species can be selected to represent the range of 
possible exposure pathways and risks. Therefore, a quanti- 
tative risk assessment performed for these indicator species 
will depict risks to the wildlife species using KR. 

Selection of indicator or key fish and wildlife species is 
based on several considerations: they are the terminus of a 
major KR food chain exposure pathway; impacts of KR on the 
species have been observed in the past; they are rare or 
endangered species; they have particularly sensitive life 
stages; or information is available on the effects of 
selenium exposure for the species. Not all of the species 
selected, of course, satisfy all of these criteria. De- 
scriptions of the selected species and rationales for their 
selection follow. 

Mallard 

The adult mallard is an omnivore with highly variable feed- 
ing habits. During nesting and egg-laying, the diet of the 
adult female changes from one relying primarily on vegeta- 
tion to one that includes more protein. Exposure during 
this period was estimated because of the potential impact on 
reproduction. The mallard duckling is probably very sensi- 
tive to selenium toxicity and its diet consists primarily of 
aquatic invertebrates. Thus, the exposure of the mallard 
duckling is probably similar to that of the tricolored 
blackbird (discussed below) . 

The mallard is an important game species in the Pacific 
flyway. Another consideration in the selection of mallards 
is the fact that there is a relatively large amount of sele- 
nium and other toxicology data available for them. 

Anterican Coot 

The adult American coot is an aquatic species with little 
dependence on the benthic community at KR. Feeding habits 
of the adult coot do not vary substantially with respect to 
sex. The adult coot feeds primarily on terrestrial and 
aquatic plants, insects, and other epiphytal fauna. 

Black-necked Stilt 

The adult black-necked stilt relies heavily on the littoral 
benthic epifauna. Stilts are wading birds that tend to eat 



SAT72/77 3-5 



11 



epifauna that they can see. Among the four species, stilts 
rely on the benthic coimnunity to the greatest extent. 

Tricolored Blackbird 

The young tricolored blackbird ( Agelaius tricolor ) (through 
fledgling) is fed almost exclusively adult insects and aqua- 
tic insect larvae. The fledgling blackbirds and stilts tend 
to rely on similar trophic levels for food, although the 
blackbird diet is not generally comprised of a significant 
amount of epibenthic species. The status of the tricolored 
blackbird as a federal candidate for threatened and endan- 
gered species listing was also a factor in its selection. 

Eared Grebe 

The eared grebe is a fish-eating bird in which KR impacts 
have been observed in the past (Ohlendorf , et al. 1986a) . 
Although the eared grebe does not exclusively eat fish, it 
was selected as a key species because fish are an important 
part of its diet and eared grebes also have limited feeding 
range, therefore, tending to have a restricted off site expo- 
sure. 

Mosquitofish 

The mosquitofish ( Gambusia itf finus ) is the only fish which 
currently exists at KR; it is highly resistant to selenium 
toxicosis. Mosquitofish were introduced into California in 
1922 and have since spread to waters throughout the state. 
The species has a worldwide distribution in warm waters due 
to its use for mosquito-control purposes. Mosquitofish are 
omnivorous and opportunistic feeders utilizing whatever or- 
ganisms are most abundant near the waters surface. The diet 
may consist of algae, zooplankton, fishes, terrestrial in- 
sects and aquatic invertebrates (Moyle 1976) . Under crowded 
conditions or periods when animal food is scarce, they may 
feed extensively on filamentous algae and diatoms (Moyle 
1976) . Mosquitofish were selected because they can survive 
with high tissue selenium levels and thus may represent a 
concentrated source of selenium. 

San Joaquin Valley Kit Fox 

The kit fox was included as the terrestrial food chain re- 
ceptor because it is a federal and state-listed endangered 
species. USFWS surveys indicate that kit foxes forage at KR 
as there have been approximately 25 confirmed observations 
of this species in the vicinity of KR since 1984. The fre- 
quency of sitings has apparently increased in the last sev- 
eral years. The kit fox diet consists of both large 
grassland animals such as rabbits, hares, California ground 
squirrels and small mammals, including California voles. 



SAT72/77 3-6 



11 



deer, mice and other small rodents. Incidental food items 
include birds, reptiles, and insects. Little data exist re- 
garding the specific diet of the kit fox in the KR area and 
the ratio of quantity of food obtained in the vicinity of KR 
to the total prey consumption of a typical kit fox is un- 
known. Furthermore, the size of the kit fox population near 
KR is not well known. USER has funded a kit fox study to 
address these issues. 

ESTIMATES OF KEY SPECIES POPULATION SIZES 

The estimates of population densities and estimates of past 
KR-related mortalities given in Table 3-1 are based on data 
from published literature, unpublished surveys by the USFWS 
and California Department of Fish and Game (DFG) , consulta- 
tion with personnel from these agencies, and other local 
experts. These data are provided to put in perspective the 
relative risks of selenium exposure of each population. 
They are not intended to indicate effects of past exposure 
to selenium at KR. The population data are indices of den- 
sity and in most cases the actual values are unknown. They 
are presented here only for the purposes of assessing the 
relative risks of fish and wildlife contamination under the 
cleanup alternatives being considered at KR. Losses given 
for KR include all sources of mortality that have been 
directly observed, including predation, disease, and chemi- 
cal-induced toxicosis. The numbers do not reflect reproduc- 
tive failures that migrant birds may experience on their 
breeding grounds that could be due to contaminants acquired 
at KR. 

As Table 3-1 suggests, the risks of contamination-induced 
mortality vary greatly between these species. The data for 
mallards suggest that this species is at low risk due to its 
small population at KR (probably due to the hazing program) 
relative to its San Joaquin Valley and statewide populations, 
Both the American coot and black-necked stilt suffered sig- 
nificant mortalities at KR during the period 1983-85, but 
small numbers of birds (4 percent) were "lost" relative to 
their San Joaquin Valley and statewide populations. In con- 
trast, the tricolored blackbird population at KR suffered an 
almost total nesting failure in 1986. Only about 100 fledg- 
lings were observed from a colony of approximately 47,000 
breeding adults. This total represents more than half the 
San Joaquin Valley population and more than one-third of the 
statewide population. The tricolored blackbird is largely 
endemic to California, so the statewide population approxi- 
mates the global population for this species (DeHaven pers. 
comm.). Preliminary USFWS data suggest the cause of this 
mortality of tricolored blackbird nestlings was due to acute 



SAT72/77 3-7 








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3-9 



selenium toxicosis from eating contaminated insects (Paveglio 
pers . comm. a) . 



ESTIMATES OF TROPHIC RELATIONSHIPS 

Trophic relationships of the key species are summarized in 
Figures 3-1 through 3-6. These ar.e based on discussions 
with ecologists familiar with KR and on studies of the ecol- 
ogy of the key species conducted elsewhere (Martin, et al. 
1951, Pough 1951, Johnsgard 1975). 



ADAPTATION FOR RISK ASSESSMENT 

Evaluation of the risk of KR cleanup alternatives to fish 
and wildlife requires, for each cleanup alternative, a pre- 
diction of the exposure of wildlife to selenium. The trans- 
fer of selenium through the food chain and concentrations of 
selenium in food groups were estimated for each cleanup al- 
ternative using empirical relationships (transfer factors) 
derived from studies conducted at KR and elsewhere. The 
empirical transfer factors served as the basis for the mathe- 
matical model used to predict the relationship between sele- 
nium in each trophic level and, ultimately, the exposure of 
key species to selenium. The model is described in Chap- 
ter 5. 

In order to model and predict selenium transfer and dietary 
exposure to the selenium transfer pathways shown in Fig- 
ures 3-1 through 3-6 were simplified. Schematic represen- 
tations of selenium transfer and exposure used for predic- 
tion purposes are shown in Figure 3-7 through 3-9. The sim- 
plified selenium transfer diagram was developed in consul- 
tation with USFWS personnel after the complex pathways were 
identified for each of the key species. 

The simplified pathways contain all of the basic selenium 
transfer pathways present in the complex transfer diagrams 

(Figures 3-1 through 3-6) . Although uptake pathways exist 
that are not depicted in the simplified transfer diagrams 

(e.g. direct uptake of dissolved selenium by herbivores and 
carnivores) , transfer factors are derived to predict the 
change in concentrations between compartments or trophic 
levels that occurs as a result of all uptake pathways. In 
other words, the concentrations of selenium in a particular 
compartment is expressed solely as function of the concen- 
trations in the adjacent compartment. 

The simplified selenium transfer diagrams contain all of the 
basic selenium compartments present in the complex pathways. 
Since data from KR show that many groups contain similar 
levels of selenium, it is not necessary to distinguish be- 
tween them for modeling purposes. For instance, there is a 



SAT72/77 3-10 



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3-19 



variety of non-rooted aquatic plants present at KR, including 
Nitella , attached diatoms, attached green algae, etc. How- 
ever, since rooted plants can acquire selenium from sediment 
and water (and selenium levels in each will be affected dif- 
ferently by each cleanup alternative) , selenium levels in 
rooted plants are expected to respond differently than non- 
rooted plants to implementation of each alternative. 

Associated with the simplified selenium transfer diagram for 
each of the key organisms are estimates of the selenium con- 
centrations in each compartment (e.g., sediment, water, non- 
rooted plants, etc.), transfer factors, and diet factors. 
Associated with each mean estimate is a variance estimate 
(plus or minus one standard deviation) that reflects empiri- 
cal variability and confidence in empirical and literature 
values. 

Important aspects of the simplified pathways, including ex- 
planations of how key values were determined, are discussed 
below. Data used to derive transfer factors and their sour- 
ces are summarized in Table 3-2. The transfer factors are 
given in Tables 3-3 through 3-5. Other important aspects of 
applicability of the simplified selenium transfer diagrams 
to risk assessment are discussed in Chapter 5. 

SEDIMENT 

Since water applied to KR will have very low selenium con- 
centration (less than 1 yg/l) , the major potential source of 
selenium for biological uptake is the soil. Selenium can 
enter the biosphere directly from selenium forms in the 
sediments or it can dissolve in water that will be present 
in the ponds as described in each alternative. 

The amount of selenium currently present in sediments is 
quite variable but tends to be greater in southern ponds 
than in northern ponds. In the FRP alternative, where no 
removal of sediment is involved, a value of 7 mg/kg ±7 
(±1 standard deviation) is used. This concentration is 
representative of the southern ponds which have relatively 
high sediment selenium concentrations (see Table 4-2, USER 
1986a) . The variance component of this estimate reflects 
the spatial heterogeneity of selenium measured at KR. After 
excavating sediment with selenium concentrations greater 
than 4 mg/kg (Onsite Disposal Plan-1) , average sediment 
selenium concentrations will be 3 mg/kg ±2. The Onsite 
Disposal Plan-2 will result in a sediment selenium concen- 
tration of 1.5 mg/kg ±1. 



SAT72/77 3-20 



11 
■ 

■ 



3 



Table 3-2 

SUMMARY OF DATA USED TO DERIVE TRANSFER FACTORS' 

(±1 STANDARD DEVIATION) 



Non-Piscivorous Bird Pathway 





Past 
Value 

7±7 




Fl^ 


exible Re 


isponse 


Onsite Disposal 




Source 

1 


Value 


Source 


Value 


Source 


Sediment 


717 


1 


3±2, 
1.511'= 




1^ 


















Rooted Plants 


26118 


1 




26118 


1 


26118 




1 


Water 


300 


1 




2-15 


2 


2-15 




2 


Non-Rooted Plants 


56±5.5 


2 




0.3-20'' 


4 


0.3-20*^ 




4 


Non-Benthic Herbivores 


127123 


2,3 




e 


4 


e 




4 


Non-Benthic Carnivores 


92119 


2,3 




2-270 


4 


2-270 




4 


Detritus 


26118 


5 




26118 


5 


26118 




5 


Detritivores 


5615.5 


2,3 




5615.5 


2,3 


56+5,5 


2 


,3 


Benthic Carnivores 


127123 


2,3 




127123 


2,3 


127+23 


2 


,3 






Fish/Piscivorous Bird 


Pathway 







Sediment 



7 + 7 



Water 

Non-Rooted Plants 



300 1 

5615.5 2 

Non-Benthic Herbivores 127123 2,3 

Mosquitofish/Carnivores 104125 2 



717 



2-1^ 
0.3-20^^ 



2-270 



1 312, 
1.5 + 1 

2 2-15 
4 0.3-20 
4 e 
4 2-270 



Terrestrial Pathway 



Soil 

Terrestrial Plants 

Herbivores 

Carnivores 



312 

30110 
10124 
48+17 



312 

30 + 10 
10124 
48117 



3 + 2,, 





1.511 


1 


30110 


6 


10124 


6 


48117 



Data Sources: 

1 USER 1986a. Standard QA/QC procedures, all data sources given in EIS. 

2 LBL 1986. LBL is developing QA/QC procedures, and therefore, 
data are not final. 

3 Ohlendorf et al. 1986. QA/QC procedures specified. 

4 Lemly 1985. QA/QC procedures not specified. 

5 No specific reference. Assumed majority of detritus comprised of 
rooted macrophytes. 

6 Clark, personal communication. 

Note: All standard deviations estimated by dividing range by 6 except 
those from LBL (1986) which were given in reference. This is 
based on the assumptions of a normal distribution and that >99% 
of values are within 13 stand, dev. 



All units mg/kg (d.w.) except water which is yg/1. 

Two values given for Onsite Disposal No. 1 and 2, respectively, 

Mean value from USBR {1986a) 

d 
Range only was given in reference. 

Q 

Inferred from reference data. 
SAT72/89 

3-21 



■ 



I* 



Table 3-3 

TRANSFER AND DIET FACTORS FOR SIMPLIFIED SELENIUM 

TRANSFER DIAGRAM FOR MALLARD, AMERICAN COOT, 

TRICOLORED BLACKBIRD, AND BLACK-NECKED STILT 

(Standard Deviations are in parentheses) 



Sediment Cone, (mg/kg d.w.) 
Surface Water Supply (mg/1) 

Transfer Factors 

1 Sediment - Rooted Plants 

2 Sediment - Water 

3 Water - Rooted Plants 

4 Water - Non-rooted Plants 

5 Non-rooted Plants - 

Herbivores 

6 Herbivores - Carnivores 

7 Sediment - Detritus/ 

Microbes 

8 Detritus/Microbes - 

Detritivores 

9 Detritivores - Carnivores 

Relative Supply Factors 

a Sediment - Rooted Plants 

b Water - Rooted Plants 

c Surface Water Supply - Water 

d Sediment - Water 



Past 
Condition 


Flexible 
Response 


Onsite ^ 
Disposal 1 


Onsite 
Disposal 2 


7 (7) 
0.3 


7 (7)^^ 



3(2) 



1.5 (1) 



2.8 (3) 

0.0003-0.002 

81 (21) 

187 (22) 


2.8 (3) 

0.0003-0.002 

81 (21) 

500 (50) 


2.8 (3) 

0.0003-0.002 

81 (21) 

500 (50) 


2.8 (3) 

0.0003-0.002 

81 (21) 

500 (50) 


2.2 (0.8) 
0.7 (0.3) 


4.0 (2.0) 
1.5 (0.5) 


4.0 (2.0) 
1.5 (0.5) 


4.0 (2.0) 
1.5 (0.5) 


2.4 (2.9) 


2.4 (2.9) 


2.4 (2.9) 


2.4 (2.9) 


2.2 (0.8) 
0.7 (0.3) 


2.2 (0.8) 
0.7 (0.3) 


2.2 (0.8) 
0.7 (0.3) 


2.2 (0.8) 
0.7 (0.3) 


25 
75 

ter 100 



25 

75 



100 


25 

75 



100 


25 

75 



100 



DIET FACTORS'^ FOR 
PAST CONDITION, FLEXIBLE RESPONSE, AND ONSITE DISPOSAL 



e Rooted Plants - Receptor 

f Water - Receptor 

g Non-rooted Plants - Receptor 

h Herbivores - Receptor 

i Carnivores (1) - Receptor 

j Detritus/Microbes - Receptor 

k Detritivores - Receptor 

1 Carnivores (2) - Receptor 

m Off site Food Sources 



Adult Female 


Adult 


Tricolored 


Adult 


Mallard 


American 


Blac)cbird 


Black-necked 


Nesting 


Coot 


Nestling 
3 (5) 


Stilt 


14 (SI 


50 (5) 





5 (2) 


5 (2) 





5 (2) 


33 (7) 


18 (3) 


2 (1) 





41 (6) 


35 (5) 


79 (8) 


38 (5) 


7 (2) 


7 (2) 


16 (5) 


7 (3) 





1 (1) 





5 (1) 





2 (1) 





38 (5) 





2 (1) 





7 (3) 















For the seasonally Wet Areas. Also applicable to FRP seasonally wet areas in the 
northern ponds. 

For ponds that will be wet all year (southern ponds). 
'^Uniform distribution, therefore range is given. 

In cases where two routes of selenium supply exist, their ratio of supply is defined. 
^Percent of total diet from each compartment. 



SAT73/40 



3-22 



^ 



Tatle 3-4 
TRANSFER AND DIET FACTORS FOR SIMPLIFIED SELDJIUM 
TRANSFER DIAGRAM FOR EARED GREBE AND MOSQUITOFISH 
(Standard Deviations are in Parentheses) 



Sediment Cone, (mg/kg d.w.) 
Surface Water Supply (mg/1) 

Transfer Factors 

1 Sediment - Water^ 

2 Water - Non-rooted Plants 

3 Non-rooted Plants - 

Herbivores 

4 Herbivores - Carnivores 



a Surface Water Supply - Water 
b Sediment - Water 



Past 
Condition 


Flexible 
Response 


0ns ite 
Disposal 1^ 


Onsite 
Disposal 2 


7 (7) 
0.3 


7 (7)^ 



3(2) 



1.5 (1) 



0.0003-0.002 
187 (22) 


0.0003-0.002 
500 (50) 


0.0003-0.002 
500 (50) 


0.0003-0.002 
500 (50) 


2.2 (0.8) 
0.7 (0.3) 


4.0 (2.0) 
1.5 (0.5) 


4.0 (2.0) 
1.5 (0.5) 


4.0 (2.0) 
1.5 (0.5) 


:er 100 
















DIET FACTORS FOR 
PAST CONDITIONS, FLEASIBLE RESPONSE, AND ONSITE DISPOSAL 

Western Mosquito- 

Grebe fish 



c Water - Receptor 10 (5) N/A 

d Carnivores (1) - Receptor 90 (5) N/A 



For the seasonally wet areas. Also applicable to FRP seasonally wet areas in the 
northern ponds. 

For ponds that will be wet all year (southern ponds). 

*^Uniform distribution, therefore range is given. 

In cases where two routes of selenium supply exist, their ratio is defined. 
N/A = Not applicable - see text. 

Percent of total diet from each compartment. 



SAT73/41 

3-23 



i 



Table 3-5 
TRANSFER AND DIET FACTORS FOR SIMPLIFIED SELENIUM 
TRANSFER DIAGRAM FOR SAN JOAQUIN VALLEY KIT FOX 
(Standard Deviations are in parentheses) 





Past 


Flexible 


Onsi 


-te 


0ns ite 




Condition 


Response 


Disposal 1° 


Disposal 2 


Sediment Cone, (mg/kg d.w.) 


3 (2) 


3 I 


[2)'^ 


3(2) 


1.5 (1) 


Surface Water Supply (mg/l) 


0.3 















Transfer Factors 














1 Soil - Terrestrial 














Plants 


10 (5) 


10 


(5) 


10 


(5) 


10 (5) 


2 Terrestrial Plants - 














Herbivores 


.3 (.3) 


.3 


(.3) 


.3 


(.3) 


.3 (.3) 


3 Herbivores - Carnivores 


4 (2) 


4 


(2) 


4 


(2) 


4 (2) 


Diet Factors'^ 














a Herbivores - Receptor 


22.5 (20) 


9 


(5) 


9 


(5) 


9 (5) 


b Carnivores - Receptor 


2.5 (2) 


1 


(1) 


1 


(1) 


1 (1) 


c Off site Food Sources 


75 (25) 


90 


(10) 


90 


(10) 


90 (10) 



For the seasonally wet areas. Also applicable to FRP seasonally wet areas in the 
northern ponds. 

For ponds that will be wet all year (southern ponds). 

^Percent of total diet from each compartment. 



SAT73/42 

3-24 



NON-PISCIVOROUS AQUATIC BIRD EXPOSURE PATHWAY 

Aquatic Pathway 

One of the three pathways of selenium transfer into and through 
the food chain is the aquatic pathway. Recent studies by 
LBL (1986) have indicated that selenium flux from sediments 
to "clean" water (less than 2 yg/l) will result in a concen- 
tration in the water column selenium concentration of between 
approximately 2 and 15 yg/1. They have found at KR that 
introduction of clean water resulted in a water column con- 
centration of less than 10 yg/1. Further, their laboratory 
experiments suggest that contaminated sediments can cause up 
to a 15 yg/l increase in water column concentration. The 
selenium concentrations in the water to be applied to KR 
will be less than 2 yg/1. Based on these data, we expect 
the selenium in the water column to be between 2 and 15 yg/1. 
The empirical relationship between the concentrations of se- 
lenium in sediments in the Flexible Response Plan (7 mg/kg) 
and those expected in the water column (2-15 yg/1) , was used 
to calculate a range of transfer factors of 0.0003-0.002. 
This range of transfer factors was used in the model to cal- 
culate water column selenium concentration for cleanup al- 
ternatives. Unlike other transfer factors it is described 
with a uniform distribution rather than the log normal dis- 
tribution associated with the other transfer factors. There- 
fore, no variance component is given. 

The transfer factor between water and non-rooted plants at 
KR ( Nitella and aufwuchs) was calculated to be 187 +22 using 
paired observations of selenium concentrations in water and 
unrooted plants. This transfer factor reflects the rela- 
tionship at a water selenium concentrations very much higher 
than is expected to result from either cleanup alternative. 
Since the uptake and metabolism of selenium probably does 
not have a linear relationship with concentrations in water, 
a transfer factor appropriate for the predicted range 
(2-15 yg/1) was derived from literature reviewed by Lemly 
(1985a) and Ohlendorf, et al. (1986). The same procedure 
was followed for derivation of other transfer factors in the 
aquatic food chain. Transfer factors derived from litera- 
ture were generally about two to three times higher than 
those observed in high water selenium concentrations at KR. 

Benthic Pathway 

The benthic epifauna and infauna can acquire selenium from 
overlying water and from sediments with which they live in 
close association. We assumed in our simplified selenium 
transfer diagram that sediments would be the major source of 
selenium available to benthic organisms since the concentra- 
tions in water are expected to decline substantially in both 



SAT72/77 3-25 



alternatives. Since the sediment selenium concentrations 
are not expected to change in the flexible response alterna- 
tive and change by only a factor of two to three (versus 10 
to 100 times in the water for the aquatic pathway) , the empi- 
rical relationship between selenium concentrations in the 
various selenium compartments (e.g., sediment, detritus, 
etc.) at KR was used to determine the selenium transfer fac- 
tors . 

Rooted Plant Pathway 

Rooted aquatic and semi-aquatic plants at KR can potentially 
acquire selenium from both sediment/soil, via the root/rhizome 
system, and water, via the leaf tissues. There are no defini- 
tive studies describing selenium uptake pathways of aquatic 
plants (Denny 1980) . However, studies involving other aquatic 
angiosperms and compounds other than selenium suggest that 
aquatic plants are somewhat opportunistic and will acquire 
ions from the most bio-available source (McRoy and Barsdate 
1970, Nicholas and Keeney 1976, Faraday and Churchill 1979, 
Brinkhuis et al. 1980, Denny 1980, Kenworthy et al. 1982). 
Sculthorpe (1967) indicates that tissues typically associated 
with nutrient translocation are reduced or vestigial in most 
aquatic angiosperms. Based on these studies, we have infer- 
red an approximate ratio of sediment to aquatic sources of 
selenixim uptake by aquatic plants of 1:3. This is shown in 
Table 3-3 as a "relative supply factor." These studies indi- 
cate that metal ions are not transported from sediments to 
the water column. 

Diets of Key Non-Piscivorous Aquatic Bird Species 

An estimate of selenium exposure requires a quantification 
of the fraction of the whole diet of each organism (diet 
factor) that is contributed by each compartment contained in 
the simplified selenium transfer diagram. A review of scien- 
tific literature was conducted for each species to quantify 
their food habits (Martin et al. 1951, Rough 1951, Johnsgard 
1975, Bellrose 1976) . Qualitative data of Ohlendorf , et al. 
(pers. comm.) support the estimates of diet factors given in 
Table 3-2. The key to the labels associated with each value 
in Table 3-2 is given in Figures 3-7 through 3-9. 

Some species had dietary preferences that changed very lit- 
tle with life stage or season. The preferences of other 
species changed substantially with season or life stage. 
Ranges of food preferences were developed, as appropriate 
for the specific life stage, sex, etc., of the four species. 

This procedure for determining these values is imperfect 
since the key species probably do not distinguish between, 
for instance, epiphytic herbivores and carnivores. In such 



SAT72/77 3-26 



m 



situations, where selection is approximately a function of 
their relative numbers and availability, the ratio of the 
relative mass of the two groups was used to estimate the 
ratio of their consumption. Mass units were used because 
selenium data are so expressed. For example, if it was de- 
termined from the literature that the diet of species X is 
50 percent (by weight) epiphytic invertebrates, data from KR 
would be used to determine their relative availability. 
Data indicate that the ratio (mass) of herbivores to carni- 
vores is approximately 5:1. The dietary percentage would be 
determined using the 5:1 ratio, as follows: 

Herbivores 5 x 0.50 = 0.42 
6 

Carnivores 1 x 0.50 = 0.08 
6 

Estimates of the variability in diet and confidence in esti- 
mates of mean dietary percentages are reflected in the vari- 
ance term associated with each mean. 

The simplified selenium transfer diagram also provides for 
consumption of uncontaminated food from areas adjacent to 
KR. This component of the diet was minimized so that "worst 
case" estimates of selenium exposure would be obtained. 

FISH/PISCIVOROUS BIRD PATHWAY 

The fish/piscivorous bird pathway was developed following a 
similar procedure to that used in the development of the 
non-piscivorous aquatic bird exposure pathway. The fish/ 
fish-eating bird pathway described in Figure 3-5 contains 
only the aquatic pathway and not the benthic or rooted plant 
pathway. The reasons for omitting the benthic pathway are 
that mosquitofish do not use the benthos, and introduction 
of fish that do use the benthos is not anticipated at KR. 
The rooted plant pathway is also not included in the simpli- 
fied selenium transfer diagram for the fish/piscivorous bird 
exposure pathway because rooted plants are not a component 
of the fish/piscivorous bird food chain. 

Fish 

Mosquitofish are included in the aquatic carnivore category 
because of their functional similarity to other members of 
the category at KR. Mosquitofish under past conditions have 
been found at KR to have similar selenium levels as that of 
other carnivores such as odonate larvae (USER 1986a, LBL 
1986) . Although mosquitofish consume some non-rooted 
plants, their selenium concentrations can be described as a 
function of selenium levels in herbivores. Therefore, the 
same transfer factors are used in the fish/piscivorous bird 



SAT72/77 3-27 



pathway as were developed for the non-piscivorous aquatic 
bird pathway. 

Birds 

The eared grebe was selected as the ultimate receptor in the 
fish/piscivorous bird pathway. The eared grebe does not 
search for food over a broad habitat range and, therefore, 
it was assumed that all of its food was obtained at KR and 
that fish constitute all of its diet. Eared grebes also 
feed on other types of organisms at KR such as soldierfly 
larvae. However, since the intent is to model exposure of a 
fish-eating bird, fish were emphasized in the model. 

TERRESTRIAL PATHWAY 

The San Joaquin kit fox population near KR is currently un- 
der study since little is known of their numbers, feeding 
range and feeding habits. However, it is possible to esti- 
mate exposure based on existing information (although stan- 
dard deviations associated with transfer and diet factors 
are large) . 

The simplified selenium transfer diagram for the kit fox is 
given in Figure 3-9. The transfer factors were derived from 
data in USER (1986a) and are given in Table 3-5. Diet fac- 
tors were estimated based on the relative abundance of 
herbivorous and carnivorous mammals which appear to consti- 
tute most of the diet of the kit fox. The fraction of the 
total diet obtained at KR was calculated by dividing the 
total estimated kit fox range (1,280 acres) into the upland 
area at KR (350 acres). The fraction obtained at KR is es- 
timated to decline in the future as management practices 
reduce kit fox feeding habitat. Uptake of selenium from 
water drunk at KR is not included and is expected to be 
small given the low dissolved selenium levels expected and 
the small quantity of water consumed relative to prey. 



SAT72/77 3-2! 



Chapter 4 
TOXICOLOGY OF SELENIUM 



INTRODUCTION 



The purpose of this analysis of selenium toxicity is to put 
into context the selenium exposure estimates generated in 
Chapter 5. Available data concerning selenium toxicity to 
key organisms at KR are reviewed to identify harmful levels 
of dietary selenium intake. This analysis is compared with 
the results of selenium exposure estimates for each cleanup 
alternative in Chapter 5. 

ENVIRONMENTAL SOURCES 

Selenium in the environment, its occurrence, biogeochemistry , 
and toxicity have been reviewed extensively (Rosenfeld and 
Beath 1964, Shamberger 1981-1983, Zingaro and Cooper 1974, 
Wilber 1980, NRC 1976, 1980, 1983, Adriano 1986, Eisler 
1985) . Selenium may become available to bioaquatic and ter- 
restrial organisms from the weathering of rocks and soils 
(Rosenfeld and Beath 1984) and the activities of man (USEPA 
1980) . Selenium in the environment may occur in numerous 
chemical forms due to the processes of oxidation and reduc- 
tion and biologically mediated transformations. However, 
the various forms of selenium are not distinguished in this 
risk assessment because the toxicity evaluation includes all 
forms of selenium. This approach is conservative relative 
to selenium toxicity because most data collected at KR de- 
scribe total selenium concentrations. The risk charac- 
terization also uses total selenium concentrations. 

BIRDS 
SELENIUM TOXICITY 

Excessive selenium has produced toxicity symptoms in numer- 
ous animal and human populations. The range of health pro- 
blems observed in birds is discussed in the following 
section. Extensive reviews of selenium toxicity in other 
animals are found in Rosenfeld and Beath (1964), NRC (1976, 
1980) , Wilber (1980) , USEPA (1980) ; and human effects are 
discussed by Shapiro (1973), and National Academy of 
Sciences (1977) . 

A summary of pertinent literature references showing a rela- 
tionship between selenium in avian diet and effects is pre- 
sented in Table 4-1. A discussion of these findings is 
presented in the following sections. 



SAT74/40 4-1 



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Selenium toxicity has been shown to occur in poultry, quail, 
and mallards from extensive studies dating back to the 
1930 's. These studies have shown toxic response to dietary 
ingestion of selenium compounds in an array of manifesta- 
tions such as reduced growth; reproductive impairment; 
embryogenic, hatchling, and adult mortality; deformities; 
and teratogenic effects. 

The early studies of chickens receiving selenium in the diet 
from cereal grains grown in seleniferous soils showed both 
reduced growth and reproductive impairment to complete fail- 
ure of hatching (Moxon 1937, Foley et al. 1937, Foley and 
Moxon 1938, Moxon and Rhian 1943). The selenium content of 
the grain has been speculated to have contained as much as 
10 mg/kg selenium in the form of selenomethionine (Heinz, et 
al. in press). The chicks produced in some studies (Franke 
and Tulley 1936) showed severe deformities and high morta- 
lity. Recent studies (Ohlendorf, et al. 1986, Ohlendorf et 
al. in press and Saiki 1986) have correlated diet selenium 
and low hatchability embryonic deformity and high mortality 
in wild birds at KR. 

The mechanism of selenium toxicity is not well understood 
(Ohlendorf, et al. 1986) . However, researchers have demon- 
strated various aspects of manifestations of avian selenium 
toxicity. 

Avian Toxicity 

Reproductive failure, reduced fecundity, and mortality of 
adults have been demonstrated using a seleniiim diet. A 
study by Heinz, et al. (in press) showed no effect on repro- 
ductive success, growth, or survival in mallards with dietary 
selenium concentrations up to 10 mg/kg. Higher doses of 
selenium show toxicity. Eleven of 12 adults died on a 
100 mg/kg diet and one drake died in the 25 mg/kg diet group. 
Females on the 25 mg/kg diet showed egg production, fertil- 
ity, and hatching success diminished significantly when com- 
pared to ducks fed with up to 10 mg/kg selenium. Survival 
of ducklings and 21-day-old body weights were reduced for 
the ducks receiving 25 mg/kg selenium selenite or 10 mg/kg 
selenomethionine. Ten and 25 mg/kg inorganic selenium and 
10 mg/kg selenomethionine showed teratogenic effects. Eggs 
containing 22.2 percent abnormal embryos were produced by 
mallards receiving 25 mg/kg sodium selenite in the diet. 
Similarly, mallards fed the 10 mg/kg organic selenium com- 
pound showed 18.3 percent abnormal embryos with many indi- 
viduals having multiple malformations such as missing or 
reduced bills, toes, eyes, and twisted legs. 



SAT74/40 4-3 



I 
I 
I 
■ 

I 
i 



H 



The Heinz study concluded that selenomethionine was more 
toxic to mallards than was selenite. Selenomethionine is 
reported as the major form of selenium in plants; thus, it 
may pose the greatest threat to herbivorous waterfowl (and 
carnivorous/omnivorous waterfowl utilizing herbivorous in- 
vertebrates/vertebrates for major food items) . 

Embryonic Effects 

Selenium compounds introduced into chick embryos produced a 
range of deformities due to necrosis of brain and spinal 
cord tissues, the optic cups and vesicles, and in limb tis- 
sues (Gruenwald 1985) . Embryonic malformations such as 
twisted necks and legs, missing appendages, absent or de- 
formed beaks, protruding eyes, and edema were observed when 
15 mg/kg selenium were introduced to the diet of chickens 
(Foley, et al. 1937, Franke , et al. 1936, Franke and Tulley 
1936). Chickens fed 7 to 9 mg/kg selenium or sodixim selenite 
produced embryos with edema of the head and neck (Ort and 
Latshaw 1978, Arnold, et al. 1973). Mallards fed 10 mg/kg 
selenium as selenomethionine or sodium selenite produced 
abnormal embryos (Heinz, et al. in prep.). The abnormali- 
ties noted in the embryos included stunted growth, swollen 
necks, hydrocephaly, and malformations such as reduced or 
absent lower bill, spoon-shaped bill, missing toes, twisted 
legs, and small or missing eyes. Control group abnormalities 
were limited to minor bill defects, stunting, and swollen 
necks . 

Shell quality as measured by the Radcliffe Index was poorer 
and duckling weight at birth was lower from eggs produced by 
mallard hens fed 25 mg/kg selenium (Heinz, et al. in press). 

Hatching Success 

Hatching success of fertile eggs has been considered the 
most sensitive measure of reproductive effect of selenium 
(Heinz, et al. in press). Ort and Latshaw (1978) identified 
5 mg/kg selenium (sodium selenite) as "borderline toxic" in 
chickens due to depression of hatching rates. Other studies 
of chickens (Ort and Latshaw 1978, Arnold, et al. 1972, 
1973) and Japanese quail (El-Begearmi, et al. 1977) showed 
reduced hatchability success when 7 to 9 mg/kg and 6 to 
12 mg/kg selenium doses respectively were fed in the diet. 
Mallards fed up to 25 mg/kg selenium (sodium selenite) showed 
no statistically significant decrease in hatchability, al- 
though some decline was noted at 25 mg/kg (Heinz, et al. in 
press) . 

FINDINGS 

The limited information demonstrating selenium toxicity in 
avian species shows that selenium concentrations of 5 mg/kg 



SAT74/40 4-4 



dry weight in the diet may have chronic toxic effects on 
chickens. The results of Heinz 's study with mallards showed 
that a 10 mg/kg concentration of selenomethionine results in 
reproductive impairment or embryonic deformities. 

There is a lack of wild bird studies using test species birds 
similar in ecological needs to the receptors at KR. Avian 
species at KR may have feeding habits, metabolic activities, 
reproductive cycles, and other important factors that would 
cause them to adversely respond to either higher or lower 
levels of selenium in the diet than observed in the few stud- 
ies conducted to date with quail, ducks, and chickens. 

Other complicating factors are related to the selenium 
transformations in the environment and food chain. For 
example, different bird species will be exposed to various 
ratios of inorganic and organic selenium (and subsequent 
toxic effects) depending upon diet preferences and prey food 
availability. There are no data available to estimate the 
effect of this unknown. 

Based on existing information, the range of harmful effect 
diet selenium concentration is estimated to be 5 to 
10 mg/kg. The "safe level" cleanup goal at KR is 3 mg/kg. 
The USFWS is currently evaluating a dosage of 4 mg/kg in an 
attempt to define more precisely the relationship between 
selenium concentrations in wildlife food and wildlife 
health. USFWS scientists hypothesize that adverse wildlife 
effects might occur at dosages as low as 5 or 4 mg/kg, but 
they have measured "background" levels of up to 3 mg/kg to- 
tal selenium (dry weight) in invertebrates at the Volta 
Wildlife Area where no biological effects have been observed. 
On this basis, the USFWS recommends 3 mg/kg for wildlife 
food pending conclusion of their field and laboratory re- 
search. 

MAMMALS 

Dose response relations showing toxicity from diet sources 
have not been reported for wild mammal species. Limited 
studies conducted using dogs and laboratory rats have shown 
a range of responses. A dosage in the range of 8 to 30 mg/kg 
dry weight in the diet may result in indications of chronic 
toxicity in mammals (Wilber 1980) . Rats and dogs exposed to 
dietary levels of 5 to 10 mg/kg dry weight selenium could be 
expected to show evidence of chronic toxicity (Anspaugh and 
Robinson 1971). Indications of chronic toxicity such as 
liver changes and heart, kidney, and spleen effects resulted 
from dietary selenium levels of 1.4 to 3.0 mg/kg dry weight. 

In the study of post weanling rats fed 1.6 to 11.2 mg/kg 
selenixim, Halvorson et al. (1966) observed no significant 



SAT74/40 4-5 



effect on growth by selenium concentrations of 1.6 to 4.8 mg/ 
kg. A diet of 6.4 mg/kg dry weight of sodium selenite or of 
seleniferous wheat caused significant growth depression, and 
death occurred in the post-weanling rats after the fourth 
week of the experiment at levels of 8.0 to 11.2 mg/kg. 
Spleen and pancreas enlargement were observed on the 6.4 and 
8-mg/kg diet, while liver weight was reduced when 9.6 or 
11.2 mg/kg selenium were fed. Earlier studies have shown a 
toxic response in rats fed 5 mg/kg in the diet (Moxon 1937, 
Franke and Painter 1938). 

As with birds, there is a lack of toxicological information 
on species similar to receptors at KR. Based on existing 
information for other mammals, the range of harmful effect 
diet selenium concentration is estimated to be 2 to 5 mg/kg. 



FISH 

There are very little data on which to base a direct esti- 
mate of a no adverse effect level of dietary selenium on 
fish (Hodson and Hilton 1983). Fish, however, are sensitive 
to direct exposure to selenium in water. 

In the development of ambient water quality criteria for 
selenivim, EPA (1980) summarized a database of 23 studies of 
eight freshwater fish species. The acute toxicity (96-hour 
LC50) values ranged from 620 to 28,500 yg/1 for the bluegill. 
Lower 96-hour LC50 concentrations of 2,100 and 5,200 yg/1 
were determined for fathead minnow fry and juveniles, respec- 
tively. During acute testing it was noted that some species 
become more sensitive with increased length of exposure be- 
yond 96 hours. EPA determined a freshwater final acute value 
of 263 yg/1. The criterion to protect freshwater aquatic 
life was set at 35 yg/l as a 24-hour average. This concen- 
tration is above expected water selenium levels at KR in the 
future. 

Bioaccummulation of selenium in the food chain has been im- 
plicated as the cause of reduced fish populations (Lemly 
1985a, 1985b, Finley 1985, Hilton, et al. 1980). An example 
from the effect of bioaccumulation was demonstrated at 
Belews Lake by Finley (1985) where mayfly nymphs ( Hexagenia 
limbata ) fed to bluegills caused pathological and behavioral 
changes. Fish at Belews Lake are surviving on a diet con- 
taining 5 to 18 mg/kg selenium (wet weight) . Studies using 
rainbow trout ( Salmo gairelneri ) have shown some adverse 
response to diets containing as little as 3 mg/kg selenium 
dry weight (Hilton, et al. 1980). Based on this very limit- 
ed information, the range of harmful effect diet selenium 
concentration for fish is estimated to be 3 to 5 mg/kg. 



SAT74/40 4-6 



i 
I 



Chapter 5 
RISK CHARACTERIZATION 



INTRODUCTION 



Estimation of the risks to fish and wildlife associated with 
KR cleanup alternatives is uncertain because of the lack of 
complete knowledge of the KR ecosystem food chains, uncer- 
tainty about the diet of key species, and uncertainty about 
the transfer factors which describe the biomagnif ication of 
selenium between food chain components along exposure path- 
ways. Estimates of uncertainty for diet factors and trans- 
fer factors for the key species were presented in Chapter 3. 

The uncertainty associated with each diet and transfer fac- 
tor is compounded with other uncertainties in the estimation 
of exposure level and increases the variability in a final 
estimate of exposure. The risk characterization provides 
estimates of this total variability through the use of a 
Monte Carlo simulation model. 



KESTERSON MONTE CARLO MODEL 

A Monte Carlo model is constructed by first building a con- 
ceptual model of the system. For KR, the model consists of 
a simplified selenium transfer model developed for each of 
the key species. These models are described in Chapter 3. 
The model simulates the selenium concentration in each 
compartment along an exposure pathway by multiplying the 
selenium concentration in the previous compartment by the 
appropriate transfer factor. Key species diet selenium con- 
centration is calculated by weighting each component of the 
diet by the appropriate diet factor. Boundary or initial 
conditions for the model are those selenium concentrations 
in KR sediments or surface water after implementation of a 
clean-up alternative. 

Each estimated transfer factor and diet factor has an assoc- 
iated standard distribution, either uniform or lognormal. 
The lognormal distribution is used to represent uncertainty 
in the transfer and diet factors because it is a common dis- 
tribution of selenium concentration data observed in nature. 
In addition, the lognormal distribution has several statis- 
tically desirable properties, such as estimating only posi- 
tive values. It is a skewed distribution that produces rare 
large values more often than does the normal distribution. 
The best estimate of the transfer and diet factors is taken 
as the mean of the distribution and the uncertainty is ex- 
pressed as a standard deviation or range. 



SAT75/7 5-1 



The model is run several hundred times with each iteration 
using new values for transfer and diet factors drawn random- 
ly from the assumed distribution for each factor. The re- 
sults of each simulation are tabulated and used to create an 
empirical frequency distribution of predicted selenium con- 
centrations in the diet of each key species. 

Simulations were run for each cleanup alternative for each 
key species. The model was also run under past conditions 
with the application of drainwater to KR. 



DISCUSSION 

MODEL RESULTS 

Figures 5-1 through 5-3 summarize results for each of the 
cleanup alternatives. The figures show the range of pre- 
dictions of selenium concentration in the diet of key 
species. Figures 5-4 through 5-10 show the results using 
historic conditions with application of drainwater. For any 
combination of cleanup alternative and key species, the 
50-percent probability level represents predicted diet sele- 
nium concentration resulting from the mean transfer and diet 
factors for that particular condition. The uncertainty of 
the exposure estimate is shown by the probability distribu- 
tion about the mean. 

As an example, consider the results of predictions of 
mallard exposure under the FRP. The 50-percent probability 
level represents a diet selenium concentration of about 
5 mg/kg (from Figure 5-1). Therefore, 50 percent of the 
predictions of diet selenium concentration are less than 
5 mg/kg, or based on the selenium transfer model and on the 
uncertainty of transfer and diet factors, the FRP has about 
a 50-percent chance of resulting in a mallard diet seleniiom 
concentration of less than 5 mg/kg. 

MODEL LIMITATIONS 

Temporal Context 

The exposure estimates for each alternative are based on 
basic assumptions regarding the steady state relationship 
between selenium concentration in sediments and the result- 
ing concentration in surface water. Although this relation- 
ship is based on existing knowledge of selenium chemistry 
and field and laboratory experiments, insufficient data have 
been collected to determine the length of time that will 
elapse until steady state conditions are achieved. The mod- 
el results do not take into account the length of time nec- 
essary to achieve steady state conditions. 



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Accuracy of Predictions 

The model does not describe uptake and loss rates of selen- 
ium by the components of the exposure pathways; rather, the 
model uses transfer and diet factors observed in the labora- 
tory and the field. The uncertainty estimates of these 
factors are based on these observations, but they do not 
necessarily simulate exact conditions at KR. 

Because insufficient information exists to develop quanti- 
tative dose-response relationship for diet selenium exposure 
for the key species at KR, the model results cannot be used 
to make quantitative estimates of the impact of cleanup 
alternatives on the exposed population. The toxicity pro- 
files, however, can be used along with model results to de- 
termine the uncertainty of the relative safety of cleanup 
alternatives . 

Applicability to Other Organisms 

Seven species that are representative of common and impor- 
tant trophic levels at KR were selected for selenium expo- 
sure evaluation. The impact of each cleanup alternative on 
each species can be considered in terms of the fraction of 
the total population that resides at KR. This is also true 
for other species that were not directly considered in the 
analysis since the trophic levels of the seven species are 
representative of those of a large number of species at KR. 
In other words, the transfer and diet factors (and associ- 
ated uncertainties) and, hence, the selenium exposure esti- 
mates have broad applicability and are not restricted to the 
seven species for which they were derived. 

Habitat Changes 

The model does not address the potential indirect effect of 
implementation of each alternative on wildlife populations 
that may result from changes in habitat. As discussed ear- 
lier, this is the primary reason why the Immobilization Plan 
is not addressed in this analysis. Each alternative will 
affect the habitat of KR to a variable and unquantified ex- 
tent. For example, implementation of Onsite-2 will reduce 
tricolored blackbird nesting habitat. Furthermore, diet 
factors may change in the case of opportunistic organisms in 
response to changes in food availability brought about by 
implementation of a particular alternative. 

IMPLICATION OF EXPOSURE PREDICTIONS 

The toxicity profiles for selenium developed in Chapter 4 
indicate the following diet (average total diet) selenium 
concentrations may result in harmful impacts: 



SAT75/7 5-13 



I 

i 



m 



Harmful Diet 

Diet Selenium Cleanup 
Concentration Goals 

Key Species Group (mg/kg) (mg/kg) 

Birds 5-10 3 

Mammals 2-5 3 

Fish 5-10 5 

Harmful diet selenium concentrations are different than 
cleanup goals because the harmful levels represent concen- 
trations that are expected to cause harm rather than the 
more conservative cleanup levels. Table 5-1 shows the per- 
cent of diet selenium predictions that are below harmful 
levels for each key species and for each cleanup alterna- 
tive. 

The risk characterization does not indicate that any of the 
plans will clearly fail. For avian species, the results for 
FRP indicate that 40 to 65 percent of the diet selenium 
predictions will be beneath harmful effect levels. It 
should be noted that the most recent results of LBL research 
at KR (LBL 1986) indicate that surface water selenium 
concentrations may be in the 2- to 5-pg/l range under the 
FRP. The model results are based on a range of 2 to 
15 yg/1. The FRP may therefore have a greater chance of 
being effective than the modeling results indicate. 

The Onsite Disposal Plan-1 shows a greater frequency of be- 
low harmful effect predictions than the FRP, 65 to 90 per- 
cent. The Onsite Disposal Plan-2 results in the highest 
frequency of below harmful effect predictions, 85 to 95 per- 
cent. 

Although the Onsite Disposal Plans show 65 to 95 percent 
average probability of diet selenium concentrations below 
the harmful effect level, these plans will be less likely to 
achieve the more conservative diet cleanup goals. For 
example. Figure 5-11 shows the relationship between the 
probability of selenium concentrations in American coot and 
black-necked stilt diets being less than 3 mg/kg versus 
residual selenium concentrations in KR soils after onsite 
disposal. These two species represent the range of predict- 
ed responses. The Onsite Disposal Plan-1 appears to have 
about a 30- to 50-percent chance of achieving receptor diet 
selenium levels less than 3 mg/kg. The Onsite Disposal 
Plan-2 has about a 55- to 85-percent chance. To achieve 
probabilities in the 90- to 100-percent range, soil residu- 
als would have to be less than 0.5 mg/kg. To achieve these 
residual levels, excavation would have to extend to greater 
than 6 inches (i.e., excavating the entire site to up to 
2 feet) . 



SAT75/7 5-14 



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5-16 



COST VERSUS RISKS 

To aid in decisionmaking, costs of cleanup alternatives can 
be compared to probability of harmful effect occurring. As 
described in Chapter 4, it is not possible to predict the 
number of individuals of various species "saved" versus cost 
under the various cleanup alternatives because quantitative 
dose response information is not available for the receptor 
species. Costs can be compared, however, to observations of 
the total number of birds "lost" in the past (see Table 3-1) . 
Costs can also be compared to predictions of diet selenium 
concentrations . 

Figure 5-12 shows the relationship between diet selenium 
concentrations for American coots and blacknecked stilts and 
costs for the three cleanup alternatives and past conditions 
at KR. This figure shows that termination of drainwater 
flow into KR and implementation of the FRP will reduce diet 
selenium concentrations by about 90 percent. However, the 
FRP still presents risks to wildlife because it may not 
achieve avian diet cleanup goals. 

Figure 5-13 compares the costs of alternative cleanup plans 
versus "effectiveness" as measured by residual soil selenium 
concentrations and by predicted average concentrations of 
selenium in avian diets. As shown by this figure, the FRP 
is predicted to achieve soil selenium concentrations of 

7 mg/kg; 50 percent of the predictions indicate that the FRP 
can achieve average avian diet selenium concentrations of 

8 mg/kg. First year costs of the FRP are $2.5 million. The 
Onsite Disposal Plan-1, for a first year expenditure of 

$20 million (8 times that of the FRP) , is predicted to 
achieve soil selenium concentrations of 3 mg/kg (a 57-percent 
reduction compared to the FRP) ; 50 percent of the predictions 
indicate this plan can achieve average avian diet selenium 
concentrations of 4 mg/kg (a 50-percent reduction compared 
to the FRP) . The Onsite Disposal Plan-2, for a first year 
capital expenditure of $40 million (16 times that of the 
FRP) , is predicted to achieve soil selenium concentrations 
of 1.5 mg/kg (a 79-percent reduction compared to the FRP) ; 
51 percent of the predictions indicate this plan can achieve 
average avian diet selenium concentrations of 2.5 mg/kg (a 
69-percent reduction compared to the FRP) . 



SAT75/7 5-17 



z 
o 

d 

2 



o 
o 




BLACK-4CCKE0 STILT 



45 



•0 



76 



90 



AVERAGE IMET SELENIUM CONCENTRATION 
FOR AMERICAN COOT t BLACK-NECKED STILT (mg/kg) 



COSTS (DOLLARS) 

FRP: 2.5 MILLION 
ONSITE-1: 20 MILLION 
ONSITE-2: M MILLION 



FIGURE 5-12 

COST VERSUS DIET SELENIUM CONCENTRATION 

FOR ALTERNATIVE CLEANUP PLANS 



5-1: 



I 



i 




2 4 6 

SOIL SELENIUM (mg/kq) 




4t P«rc«ntag*8 r«f«r to chanc* 
of average avian diet being 
less than Y-axis value. 



FIGURE 6-13 

COSTS OF ALTERNATIVE CLEANUP 
PLANS VERSUS SOIL & DIET SELENIUM 



5-19 



•CHMHIIL- 



I 



Chapter 6 
REFERENCES 



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Burau, R.G. 1985. Environmental chemistry of selenium. 
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I 
I 






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Landauer, W. 1952. Malformations of chicken embryos produced 
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Moyle, P.B. 1976. Inland Fishes of California. Berkeley, 
California: University of California Press. 405 pp. 



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SAT74/56 6-5 



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Zingaro, R.A. and W.C. Cooper (eds.). 1974. Selenium. New 
York. Van Nostrand Reinhold Company. 835 pp. 



PERSONAL COMMUNICATION 

Daniel, Dick. 1985. Environmental Services Supervisor, 
Department of Fish and Game, Sacramento, CA 1985. Unpub- 
lished data. 

DeHaven, Richard. April 1986. Environmental Services, U.S. 
Fish and Wildlife Service, Sacramento, CA. Telephone 
conversaion. 

Gould, G. November 7, 1986. Biologist. California Depart- 
ment of Fish and Game, Sacramento, CA. Telephone conversa- 
tion. 

Kizer, K.W. October 18 and 23, 1984. Director. California 
State Department of Health Services, Sacramento, CA. Memo- 
randum to Jack Parnell, Director, Department of Fish and 
Game, and letter. 



SAT74/56 6-6 



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i 



Ohlendorf, Harry. December 1985 and January, February, Sep- 
tember, 1986. Research Biologist. U.S. Fish and Wildlife 
Service, Pacific Coast Field Station, Patuxent Wildlife Re- 
search Center, Dixon, California. 

Paveglio, Fred. January and November 1986. Refuge Biologist. 
Kesterson National Wildlife Refuge, Los Bancs, CA. Telephone 
conversations and meetings. 



SAT74/56 6-7 



APPENDIX A 



Appendix A 

Kesterson Reservoir 

Wildlife Species List 



Common Name 



Scientific Name 



Mammals 

Virginia opossum 
Ornate shrew 
Marsh shrew 
Broad-footed mole 
Bat species 



Desert cottontail 

Black-tailed hare 

California ground squirrel 

Botta ' s pocket gopher 

San Joaquin pocket mouse 

Heermann's kangaroo rat 

Fresno kangaroo rat 

Short-nosed kangaroo rat 

Western harvest mouse 

Deer mouse 

Muskrat 

California vole 

House mouse 

Coyote 

San Joaquin kit fox 

Raccoon 

Long-tailed weasel 

Mink 

Badger 

Western spotted skunk 

Striped skunk 

Birds 



Didelphis Virginia 

Sorex ornatus 

S. bendirii 

Scapanus latimanus 

Myotis spp. , Lasiurus spp. 

Eptesicus spp. 

Pipistrellus spp. 

Sylvilagus audubonii 

Lepus californicus 

Spermophilus beecheyi 

Thomomys bottae 

Perognathus inornatus inornatus 

Dipodomys heermanni 

D. nitratoides exilis 

D. n. brevinasus 

Reithrodontomys megalotis 

Peromyscus maniculatus 

Ondatra zibethicus 

Microtus californicus 

Mus musculus 

Canis latrans 

Vulpes macrotis mutica 

Procyon lotor 

Mustela frenata 

M, 



vxson 



Taxidea taxus 
Spilogale gracilis 
Mephitis mephitis 



Pied-billed grebe 
Horned grebe 
Eared grebe 
Western grebe 
American white pelican 
Double-crested cormorant 
American bittern 
Great blue heron 
Great egret 
Snowy egret 
Cattle egret 



Podilymbus podiceps 
Podiceps auritus 
P. nigricollis 
Aechmophorus occidentalis 
Pelecanus erythrorhynchos 
Phalacrocorax auritus 
Botaurus lentiginosus 
Ardea herodias 
Casmerodius albus 
Egretta thula 
Bubulcus ibis 



SAT 7 3/7 3 



Appendix A 
(Continued) 



Common Name 



Scientific Name 



Birds (continued) 



Green-backed heron 

Black-crowned night-heron 

White-faced ibis 

Tundra swan 

Greater white-fronted goose 

Snow goose 

Ross' goose 

Canada goose 

Green-winged teal 

Mallard 

Northern pintail 

Blue-winged teal 

Cinnamon teal 

Northern shoveler 

Gadwall 

Eurasian wigeon 

American wigeon 

Canvasback 

Redhead 

Ring-necked duck 

Greater scaup 

Lesser scaup 

Common goldeneye 

Buff lehead 

Hooded merganser 

Common merganser 

Ruddy duck 

Turkey vulture 

Osprey 

Black-shouldered kite 

Bald eagle 

Northern harrier 

Cooper ' s hawk 

Sharp-shinned hawk 

Swainson ' s hawk 

Red- tailed hawk 

Ferruginous hawk 

Rough-legged hawk 

Golden eagle 

American kestrel 

Prairie falcon 

Ring-necked pheasant 

Virginia rail 

Sora 

Common moorhen 



Butorides striatus 
Nycticorax nycticorax 
Plegadis chihi 
Cygnus columbianus 
Anser albifrons 
Chen caerulescens 
C. rossii 



Branta canadensis 

Anas crecca 

A. platyrhynchos 

A. acuta 

A. discors 

A. cyanoptera 

A. clypeata 

A. strepera 

A. penelope 

A. americana 

Aythya valisineria 

A. americana 

A. collaris 

A. marila 

A. af finis 
Bucephala clangula 

B. albeola 

Lophodytes cucullatus 
Mergus merganser 
Oxyura jamaicensis 
Cathartes aura 
Pandion haliaetus 
Elanus caeruleus 
Haliaeetus leucocephalus 
Circus cyaneus 
Accipiter cooperii 

A. striatus 

B. swainsoni 
B. jamaicensis 
B. regalis 

B. lagopus 
Aquila chrysaetos 
Falco sparverius 
F. mexicanus 
Phasianus colchicus 
Rallus limicola 
Porzana Carolina 
Gallinula chloropus 



SAT73/73 



I 
I 
I 
I 
I 
I 
I 
I 
I 
I 
I 
I 



Appendix A 
(Continued) 



Common Name 



Scientific Name 



Birds (continued) 



American coot 
Sandhill crane 
Black-bellied plover 
Snowy plover 
Semipalmated plover 
Killdeer 

Black-necked stilt 
American avocet 
Greater yellowlegs 
Lesser yellowlegs 
Willet 

Spotted sandpiper 
Whimbrel 

Long-billed curlew 
Marbled godwit 
Western sandpiper 
Least sandpiper 
Baird's sandpiper 
Pectoral sandpiper 
Dunlin 

Short-billed dowitcher 
Long-billed dowitcher 
Common snipe 
Wilson's phalarope 
Red-necked phalarope 
Bonaparte's gull 
Ring-billed gull 
California gull 
Herring gull 
Caspian tern 
Forster's tern 
Black tern 
Rock dove 
Mourning dove 
Common barn-owl 
Great horned owl 
Burrowing owl 
Short-eared owl 
Lesser nighthawk 
Belted kingfisher 
Northern flicker 
Black phoebe 
Say ' s phoebe 
Western kingbird 
Horned lark 
Tree swallow 



Fulica americana 

Grus canadensis 

Pluvialis squatarola 

Charadrius alexandrinus 

C. semipalmatus 

C. vociferus 

Himantopus mexicanus 

Recurvirostra americana 

Tringa melanoleuca 

T. f lavipes 

Ca toptr ophorus semipalmatus 

Actitus macularia 

Numenius phaeopus 

N. americanus 

Limosa fedoa 

Calidris mauri 

C. minutilla 

C. bairdii 

C. melanotos 

C. alpina 

Limnodromus griseus 

L. scolopaceus 

Gallinago gallinago 

Phalaropus tricolor 

P. fulicaria 

Larus Philadelphia 

L. delawarensis 

L, 

L. 



californicus 



argentatus 
Sterna caspia 
S. forsteri 
Chidonias niger 
Columba livia 
Zenaida macroura 
Tyto alba 
Bubo virginianus 
Athene cunicularia 
Asio f lammeus 
Chordeiles acutipennis 
Ceryle alcyon 
Colaptes auratus 
Sayornis nigricans 
S. saya 

Tyrannus verticalis 
Eremophila alpestris 
Tachycineta bicolor 



SAT73/73 



Appendix A 
(Continued) 



Common Name 



Birds (continued) 



Scientific Name 



Violet-green swallow 
Northern rough-winged swallow 
Cliff swallow 
Barn swallow 
Yellow-billed magpie 
American crow 
Marsh wren 
American robin 
Water pipit 
Loggerhead shrike 
European starling 
Yellow-rumped warbler 
Common yellowthroat 
Lark sparrow 
Savannah sparrow 
Grasshopper sparrow 
Song sparrow 
Lincoln's sparrow 
Golden-crowned sparrow 
White-crowned sparrow 
Dark-eyed junco 
Red-winged blackbird 
Tricolored blackbird 
Western meadowlark 
Yellow-headed blackbird 
Brewer's blacJdbird 
Brown-headed cowbird 
House finch 
House sparrow 



T. thalassina 

Stelgidopteryx serripennis 
Hirundo pyrrhonota 
H. rustica 
Pica nuttailli 
Corvus brachrhynchos 
Cistothorus palustris 
Turdus migratorius 
An thus spinoletta 
Lanius ludovicianus 
Sturnus vulgaris 
Dendroica coronata 
Geothlypis trichas 
Chondestes grammacus 
Passerculus sandwichensis 
Ammodramus savannarum 
Melospiza melodia 
M. lincolnii 
Zonotrichia atricapilla 
Z. leucophrys 
Junco hyemalis 
Agelaius phoeniceus 
A, tricolor 
Sturnella neglecta 
Xanthocephalus xanthocephalus 
Euphagus cyanocephalus 
Molothrus ater 
Carpodacus mexicanus 
Passer domesticus 



Nomenclature follows Laudenslayer and Grenfell (1983). 



SAT73/73 



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